338 lines
11 KiB
C++
338 lines
11 KiB
C++
// auto_ptr implementation -*- C++ -*-
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// Copyright (C) 2007-2020 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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/** @file backward/auto_ptr.h
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* This is an internal header file, included by other library headers.
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* Do not attempt to use it directly. @headername{memory}
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*/
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#ifndef _BACKWARD_AUTO_PTR_H
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#define _BACKWARD_AUTO_PTR_H 1
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#include <bits/c++config.h>
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#include <debug/debug.h>
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namespace std _GLIBCXX_VISIBILITY(default)
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{
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_GLIBCXX_BEGIN_NAMESPACE_VERSION
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/**
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* A wrapper class to provide auto_ptr with reference semantics.
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* For example, an auto_ptr can be assigned (or constructed from)
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* the result of a function which returns an auto_ptr by value.
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*
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* All the auto_ptr_ref stuff should happen behind the scenes.
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*/
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template<typename _Tp1>
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struct auto_ptr_ref
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{
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_Tp1* _M_ptr;
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explicit
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auto_ptr_ref(_Tp1* __p): _M_ptr(__p) { }
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} _GLIBCXX_DEPRECATED;
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
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/**
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* @brief A simple smart pointer providing strict ownership semantics.
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*
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* The Standard says:
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* <pre>
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* An @c auto_ptr owns the object it holds a pointer to. Copying
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* an @c auto_ptr copies the pointer and transfers ownership to the
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* destination. If more than one @c auto_ptr owns the same object
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* at the same time the behavior of the program is undefined.
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*
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* The uses of @c auto_ptr include providing temporary
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* exception-safety for dynamically allocated memory, passing
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* ownership of dynamically allocated memory to a function, and
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* returning dynamically allocated memory from a function. @c
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* auto_ptr does not meet the CopyConstructible and Assignable
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* requirements for Standard Library <a
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* href="tables.html#65">container</a> elements and thus
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* instantiating a Standard Library container with an @c auto_ptr
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* results in undefined behavior.
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* </pre>
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* Quoted from [20.4.5]/3.
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*
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* Good examples of what can and cannot be done with auto_ptr can
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* be found in the libstdc++ testsuite.
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*
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* _GLIBCXX_RESOLVE_LIB_DEFECTS
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* 127. auto_ptr<> conversion issues
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* These resolutions have all been incorporated.
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*/
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template<typename _Tp>
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class auto_ptr
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{
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private:
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_Tp* _M_ptr;
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public:
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/// The pointed-to type.
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typedef _Tp element_type;
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/**
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* @brief An %auto_ptr is usually constructed from a raw pointer.
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* @param __p A pointer (defaults to NULL).
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*
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* This object now @e owns the object pointed to by @a __p.
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*/
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explicit
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auto_ptr(element_type* __p = 0) throw() : _M_ptr(__p) { }
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/**
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* @brief An %auto_ptr can be constructed from another %auto_ptr.
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* @param __a Another %auto_ptr of the same type.
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*
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* This object now @e owns the object previously owned by @a __a,
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* which has given up ownership.
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*/
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auto_ptr(auto_ptr& __a) throw() : _M_ptr(__a.release()) { }
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/**
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* @brief An %auto_ptr can be constructed from another %auto_ptr.
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* @param __a Another %auto_ptr of a different but related type.
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*
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* A pointer-to-Tp1 must be convertible to a
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* pointer-to-Tp/element_type.
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*
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* This object now @e owns the object previously owned by @a __a,
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* which has given up ownership.
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*/
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template<typename _Tp1>
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auto_ptr(auto_ptr<_Tp1>& __a) throw() : _M_ptr(__a.release()) { }
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/**
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* @brief %auto_ptr assignment operator.
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* @param __a Another %auto_ptr of the same type.
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*
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* This object now @e owns the object previously owned by @a __a,
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* which has given up ownership. The object that this one @e
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* used to own and track has been deleted.
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*/
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auto_ptr&
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operator=(auto_ptr& __a) throw()
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{
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reset(__a.release());
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return *this;
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}
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/**
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* @brief %auto_ptr assignment operator.
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* @param __a Another %auto_ptr of a different but related type.
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*
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* A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type.
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*
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* This object now @e owns the object previously owned by @a __a,
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* which has given up ownership. The object that this one @e
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* used to own and track has been deleted.
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*/
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template<typename _Tp1>
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auto_ptr&
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operator=(auto_ptr<_Tp1>& __a) throw()
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{
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reset(__a.release());
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return *this;
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}
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/**
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* When the %auto_ptr goes out of scope, the object it owns is
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* deleted. If it no longer owns anything (i.e., @c get() is
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* @c NULL), then this has no effect.
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*
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* The C++ standard says there is supposed to be an empty throw
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* specification here, but omitting it is standard conforming. Its
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* presence can be detected only if _Tp::~_Tp() throws, but this is
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* prohibited. [17.4.3.6]/2
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*/
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~auto_ptr() { delete _M_ptr; }
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/**
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* @brief Smart pointer dereferencing.
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*
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* If this %auto_ptr no longer owns anything, then this
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* operation will crash. (For a smart pointer, <em>no longer owns
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* anything</em> is the same as being a null pointer, and you know
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* what happens when you dereference one of those...)
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*/
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element_type&
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operator*() const throw()
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{
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__glibcxx_assert(_M_ptr != 0);
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return *_M_ptr;
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}
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/**
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* @brief Smart pointer dereferencing.
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*
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* This returns the pointer itself, which the language then will
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* automatically cause to be dereferenced.
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*/
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element_type*
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operator->() const throw()
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{
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__glibcxx_assert(_M_ptr != 0);
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return _M_ptr;
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}
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/**
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* @brief Bypassing the smart pointer.
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* @return The raw pointer being managed.
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*
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* You can get a copy of the pointer that this object owns, for
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* situations such as passing to a function which only accepts
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* a raw pointer.
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*
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* @note This %auto_ptr still owns the memory.
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*/
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element_type*
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get() const throw() { return _M_ptr; }
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/**
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* @brief Bypassing the smart pointer.
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* @return The raw pointer being managed.
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*
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* You can get a copy of the pointer that this object owns, for
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* situations such as passing to a function which only accepts
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* a raw pointer.
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*
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* @note This %auto_ptr no longer owns the memory. When this object
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* goes out of scope, nothing will happen.
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*/
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element_type*
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release() throw()
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{
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element_type* __tmp = _M_ptr;
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_M_ptr = 0;
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return __tmp;
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}
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/**
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* @brief Forcibly deletes the managed object.
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* @param __p A pointer (defaults to NULL).
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*
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* This object now @e owns the object pointed to by @a __p. The
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* previous object has been deleted.
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*/
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void
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reset(element_type* __p = 0) throw()
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{
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if (__p != _M_ptr)
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{
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delete _M_ptr;
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_M_ptr = __p;
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}
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}
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/**
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* @brief Automatic conversions
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*
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* These operations are supposed to convert an %auto_ptr into and from
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* an auto_ptr_ref automatically as needed. This would allow
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* constructs such as
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* @code
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* auto_ptr<Derived> func_returning_auto_ptr(.....);
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* ...
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* auto_ptr<Base> ptr = func_returning_auto_ptr(.....);
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* @endcode
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*
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* But it doesn't work, and won't be fixed. For further details see
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* http://cplusplus.github.io/LWG/lwg-closed.html#463
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*/
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auto_ptr(auto_ptr_ref<element_type> __ref) throw()
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: _M_ptr(__ref._M_ptr) { }
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auto_ptr&
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operator=(auto_ptr_ref<element_type> __ref) throw()
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{
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if (__ref._M_ptr != this->get())
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{
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delete _M_ptr;
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_M_ptr = __ref._M_ptr;
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}
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return *this;
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}
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template<typename _Tp1>
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operator auto_ptr_ref<_Tp1>() throw()
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{ return auto_ptr_ref<_Tp1>(this->release()); }
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template<typename _Tp1>
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operator auto_ptr<_Tp1>() throw()
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{ return auto_ptr<_Tp1>(this->release()); }
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} _GLIBCXX_DEPRECATED;
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// _GLIBCXX_RESOLVE_LIB_DEFECTS
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// 541. shared_ptr template assignment and void
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template<>
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class auto_ptr<void>
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{
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public:
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typedef void element_type;
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} _GLIBCXX_DEPRECATED;
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#if __cplusplus >= 201103L
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template<_Lock_policy _Lp>
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template<typename _Tp>
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inline
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__shared_count<_Lp>::__shared_count(std::auto_ptr<_Tp>&& __r)
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: _M_pi(new _Sp_counted_ptr<_Tp*, _Lp>(__r.get()))
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{ __r.release(); }
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template<typename _Tp, _Lock_policy _Lp>
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template<typename _Tp1, typename>
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inline
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__shared_ptr<_Tp, _Lp>::__shared_ptr(std::auto_ptr<_Tp1>&& __r)
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: _M_ptr(__r.get()), _M_refcount()
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{
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__glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
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static_assert( sizeof(_Tp1) > 0, "incomplete type" );
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_Tp1* __tmp = __r.get();
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_M_refcount = __shared_count<_Lp>(std::move(__r));
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_M_enable_shared_from_this_with(__tmp);
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}
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template<typename _Tp>
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template<typename _Tp1, typename>
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inline
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shared_ptr<_Tp>::shared_ptr(std::auto_ptr<_Tp1>&& __r)
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: __shared_ptr<_Tp>(std::move(__r)) { }
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template<typename _Tp, typename _Dp>
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template<typename _Up, typename>
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inline
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unique_ptr<_Tp, _Dp>::unique_ptr(auto_ptr<_Up>&& __u) noexcept
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: _M_t(__u.release(), deleter_type()) { }
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#endif
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#pragma GCC diagnostic pop
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_GLIBCXX_END_NAMESPACE_VERSION
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} // namespace
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#endif /* _BACKWARD_AUTO_PTR_H */
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