// auto_ptr implementation -*- C++ -*- // Copyright (C) 2007 Free Software Foundation, Inc. // // This file is part of the GNU ISO C++ Library. This library is free // software; you can redistribute it and/or modify it under the // terms of the GNU General Public License as published by the // Free Software Foundation; either version 2, or (at your option) // any later version. // This library is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // You should have received a copy of the GNU General Public License // along with this library; see the file COPYING. If not, write to // the Free Software Foundation, 51 Franklin Street, Fifth Floor, // Boston, MA 02110-1301, USA. // As a special exception, you may use this file as part of a free software // library without restriction. Specifically, if other files instantiate // templates or use macros or inline functions from this file, or you compile // this file and link it with other files to produce an executable, this // file does not by itself cause the resulting executable to be covered by // the GNU General Public License. This exception does not however // invalidate any other reasons why the executable file might be covered by // the GNU General Public License. /** @file stl_auto_ptr.h * This is an internal header file, included by other library headers. * You should not attempt to use it directly. */ #ifndef _STL_AUTO_PTR_H #define _STL_AUTO_PTR_H 1 #include #include _GLIBCXX_BEGIN_NAMESPACE(std) /** * A wrapper class to provide auto_ptr with reference semantics. * For example, an auto_ptr can be assigned (or constructed from) * the result of a function which returns an auto_ptr by value. * * All the auto_ptr_ref stuff should happen behind the scenes. */ template struct auto_ptr_ref { _Tp1* _M_ptr; explicit auto_ptr_ref(_Tp1* __p): _M_ptr(__p) { } }; /** * @brief A simple smart pointer providing strict ownership semantics. * * The Standard says: * 
   *  An @c auto_ptr owns the object it holds a pointer to.  Copying
   *  an @c auto_ptr copies the pointer and transfers ownership to the
   *  destination.  If more than one @c auto_ptr owns the same object
   *  at the same time the behavior of the program is undefined.
   *
   *  The uses of @c auto_ptr include providing temporary
   *  exception-safety for dynamically allocated memory, passing
   *  ownership of dynamically allocated memory to a function, and
   *  returning dynamically allocated memory from a function.  @c
   *  auto_ptr does not meet the CopyConstructible and Assignable
   *  requirements for Standard Library container elements and thus
   *  instantiating a Standard Library container with an @c auto_ptr
   *  results in undefined behavior.
   *
* Quoted from [20.4.5]/3. * * Good examples of what can and cannot be done with auto_ptr can * be found in the libstdc++ testsuite. * * @if maint * _GLIBCXX_RESOLVE_LIB_DEFECTS * 127. auto_ptr<> conversion issues * These resolutions have all been incorporated. * @endif */ template class auto_ptr { private: _Tp* _M_ptr; public: /// The pointed-to type. typedef _Tp element_type; /** * @brief An %auto_ptr is usually constructed from a raw pointer. * @param p A pointer (defaults to NULL). * * This object now @e owns the object pointed to by @a p. */ explicit auto_ptr(element_type* __p = 0) throw() : _M_ptr(__p) { } /** * @brief An %auto_ptr can be constructed from another %auto_ptr. * @param a Another %auto_ptr of the same type. * * This object now @e owns the object previously owned by @a a, * which has given up ownsership. */ auto_ptr(auto_ptr& __a) throw() : _M_ptr(__a.release()) { } /** * @brief An %auto_ptr can be constructed from another %auto_ptr. * @param a Another %auto_ptr of a different but related type. * * A pointer-to-Tp1 must be convertible to a * pointer-to-Tp/element_type. * * This object now @e owns the object previously owned by @a a, * which has given up ownsership. */ template auto_ptr(auto_ptr<_Tp1>& __a) throw() : _M_ptr(__a.release()) { } /** * @brief %auto_ptr assignment operator. * @param a Another %auto_ptr of the same type. * * This object now @e owns the object previously owned by @a a, * which has given up ownsership. The object that this one @e * used to own and track has been deleted. */ auto_ptr& operator=(auto_ptr& __a) throw() { reset(__a.release()); return *this; } /** * @brief %auto_ptr assignment operator. * @param a Another %auto_ptr of a different but related type. * * A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type. * * This object now @e owns the object previously owned by @a a, * which has given up ownsership. The object that this one @e * used to own and track has been deleted. */ template auto_ptr& operator=(auto_ptr<_Tp1>& __a) throw() { reset(__a.release()); return *this; } /** * When the %auto_ptr goes out of scope, the object it owns is * deleted. If it no longer owns anything (i.e., @c get() is * @c NULL), then this has no effect. * * @if maint * The C++ standard says there is supposed to be an empty throw * specification here, but omitting it is standard conforming. Its * presence can be detected only if _Tp::~_Tp() throws, but this is * prohibited. [17.4.3.6]/2 * @endif */ ~auto_ptr() { delete _M_ptr; } /** * @brief Smart pointer dereferencing. * * If this %auto_ptr no longer owns anything, then this * operation will crash. (For a smart pointer, "no longer owns * anything" is the same as being a null pointer, and you know * what happens when you dereference one of those...) */ element_type& operator*() const throw() { _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0); return *_M_ptr; } /** * @brief Smart pointer dereferencing. * * This returns the pointer itself, which the language then will * automatically cause to be dereferenced. */ element_type* operator->() const throw() { _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0); return _M_ptr; } /** * @brief Bypassing the smart pointer. * @return The raw pointer being managed. * * You can get a copy of the pointer that this object owns, for * situations such as passing to a function which only accepts * a raw pointer. * * @note This %auto_ptr still owns the memory. */ element_type* get() const throw() { return _M_ptr; } /** * @brief Bypassing the smart pointer. * @return The raw pointer being managed. * * You can get a copy of the pointer that this object owns, for * situations such as passing to a function which only accepts * a raw pointer. * * @note This %auto_ptr no longer owns the memory. When this object * goes out of scope, nothing will happen. */ element_type* release() throw() { element_type* __tmp = _M_ptr; _M_ptr = 0; return __tmp; } /** * @brief Forcibly deletes the managed object. * @param p A pointer (defaults to NULL). * * This object now @e owns the object pointed to by @a p. The * previous object has been deleted. */ void reset(element_type* __p = 0) throw() { if (__p != _M_ptr) { delete _M_ptr; _M_ptr = __p; } } /** * @brief Automatic conversions * * These operations convert an %auto_ptr into and from an auto_ptr_ref * automatically as needed. This allows constructs such as * @code * auto_ptr func_returning_auto_ptr(.....); * ... * auto_ptr ptr = func_returning_auto_ptr(.....); * @endcode */ auto_ptr(auto_ptr_ref __ref) throw() : _M_ptr(__ref._M_ptr) { } auto_ptr& operator=(auto_ptr_ref __ref) throw() { if (__ref._M_ptr != this->get()) { delete _M_ptr; _M_ptr = __ref._M_ptr; } return *this; } template operator auto_ptr_ref<_Tp1>() throw() { return auto_ptr_ref<_Tp1>(this->release()); } template operator auto_ptr<_Tp1>() throw() { return auto_ptr<_Tp1>(this->release()); } }; // _GLIBCXX_RESOLVE_LIB_DEFECTS // 541. shared_ptr template assignment and void template<> class auto_ptr { public: typedef void element_type; }; _GLIBCXX_END_NAMESPACE #endif /* _STL_AUTO_PTR_H */