1 // auto_ptr implementation -*- C++ -*-
3 // Copyright (C) 2007-2024 Free Software Foundation, Inc.
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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}
30 #ifndef _BACKWARD_AUTO_PTR_H
31 #define _BACKWARD_AUTO_PTR_H 1
33 #include <bits/c++config.h>
34 #include <debug/debug.h>
36 namespace std
_GLIBCXX_VISIBILITY(default)
38 _GLIBCXX_BEGIN_NAMESPACE_VERSION
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.
45 * All the auto_ptr_ref stuff should happen behind the scenes.
47 template<typename _Tp1
>
53 auto_ptr_ref(_Tp1
* __p
): _M_ptr(__p
) { }
54 } _GLIBCXX11_DEPRECATED
;
56 #pragma GCC diagnostic push
57 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
60 * @brief A simple smart pointer providing strict ownership semantics.
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.
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.
79 * Quoted from [20.4.5]/3.
81 * Good examples of what can and cannot be done with auto_ptr can
82 * be found in the libstdc++ testsuite.
84 * _GLIBCXX_RESOLVE_LIB_DEFECTS
85 * 127. auto_ptr<> conversion issues
86 * These resolutions have all been incorporated.
89 * @deprecated Deprecated in C++11, no longer in the standard since C++17.
90 * Use `unique_ptr` instead.
92 template<typename _Tp
>
99 /// The pointed-to type.
100 typedef _Tp element_type
;
103 * @brief An %auto_ptr is usually constructed from a raw pointer.
104 * @param __p A pointer (defaults to NULL).
106 * This object now @e owns the object pointed to by @a __p.
109 auto_ptr(element_type
* __p
= 0) throw() : _M_ptr(__p
) { }
112 * @brief An %auto_ptr can be constructed from another %auto_ptr.
113 * @param __a Another %auto_ptr of the same type.
115 * This object now @e owns the object previously owned by @a __a,
116 * which has given up ownership.
118 auto_ptr(auto_ptr
& __a
) throw() : _M_ptr(__a
.release()) { }
121 * @brief An %auto_ptr can be constructed from another %auto_ptr.
122 * @param __a Another %auto_ptr of a different but related type.
124 * A pointer-to-Tp1 must be convertible to a
125 * pointer-to-Tp/element_type.
127 * This object now @e owns the object previously owned by @a __a,
128 * which has given up ownership.
130 template<typename _Tp1
>
131 auto_ptr(auto_ptr
<_Tp1
>& __a
) throw() : _M_ptr(__a
.release()) { }
134 * @brief %auto_ptr assignment operator.
135 * @param __a Another %auto_ptr of the same type.
137 * This object now @e owns the object previously owned by @a __a,
138 * which has given up ownership. The object that this one @e
139 * used to own and track has been deleted.
142 operator=(auto_ptr
& __a
) throw()
144 reset(__a
.release());
149 * @brief %auto_ptr assignment operator.
150 * @param __a Another %auto_ptr of a different but related type.
152 * A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type.
154 * This object now @e owns the object previously owned by @a __a,
155 * which has given up ownership. The object that this one @e
156 * used to own and track has been deleted.
158 template<typename _Tp1
>
160 operator=(auto_ptr
<_Tp1
>& __a
) throw()
162 reset(__a
.release());
167 * When the %auto_ptr goes out of scope, the object it owns is
168 * deleted. If it no longer owns anything (i.e., @c get() is
169 * @c NULL), then this has no effect.
171 * The C++ standard says there is supposed to be an empty throw
172 * specification here, but omitting it is standard conforming. Its
173 * presence can be detected only if _Tp::~_Tp() throws, but this is
174 * prohibited. [17.4.3.6]/2
176 ~auto_ptr() { delete _M_ptr
; }
179 * @brief Smart pointer dereferencing.
181 * If this %auto_ptr no longer owns anything, then this
182 * operation will crash. (For a smart pointer, <em>no longer owns
183 * anything</em> is the same as being a null pointer, and you know
184 * what happens when you dereference one of those...)
187 operator*() const throw()
189 __glibcxx_assert(_M_ptr
!= 0);
194 * @brief Smart pointer dereferencing.
196 * This returns the pointer itself, which the language then will
197 * automatically cause to be dereferenced.
200 operator->() const throw()
202 __glibcxx_assert(_M_ptr
!= 0);
207 * @brief Bypassing the smart pointer.
208 * @return The raw pointer being managed.
210 * You can get a copy of the pointer that this object owns, for
211 * situations such as passing to a function which only accepts
214 * @note This %auto_ptr still owns the memory.
217 get() const throw() { return _M_ptr
; }
220 * @brief Bypassing the smart pointer.
221 * @return The raw pointer being managed.
223 * You can get a copy of the pointer that this object owns, for
224 * situations such as passing to a function which only accepts
227 * @note This %auto_ptr no longer owns the memory. When this object
228 * goes out of scope, nothing will happen.
233 element_type
* __tmp
= _M_ptr
;
239 * @brief Forcibly deletes the managed object.
240 * @param __p A pointer (defaults to NULL).
242 * This object now @e owns the object pointed to by @a __p. The
243 * previous object has been deleted.
246 reset(element_type
* __p
= 0) throw()
256 * @brief Automatic conversions
258 * These operations are supposed to convert an %auto_ptr into and from
259 * an auto_ptr_ref automatically as needed. This would allow
262 * auto_ptr<Derived> func_returning_auto_ptr(.....);
264 * auto_ptr<Base> ptr = func_returning_auto_ptr(.....);
267 * But it doesn't work, and won't be fixed. For further details see
268 * http://cplusplus.github.io/LWG/lwg-closed.html#463
270 auto_ptr(auto_ptr_ref
<element_type
> __ref
) throw()
271 : _M_ptr(__ref
._M_ptr
) { }
274 operator=(auto_ptr_ref
<element_type
> __ref
) throw()
276 if (__ref
._M_ptr
!= this->get())
279 _M_ptr
= __ref
._M_ptr
;
284 template<typename _Tp1
>
285 operator auto_ptr_ref
<_Tp1
>() throw()
286 { return auto_ptr_ref
<_Tp1
>(this->release()); }
288 template<typename _Tp1
>
289 operator auto_ptr
<_Tp1
>() throw()
290 { return auto_ptr
<_Tp1
>(this->release()); }
291 } _GLIBCXX11_DEPRECATED_SUGGEST("std::unique_ptr");
293 // _GLIBCXX_RESOLVE_LIB_DEFECTS
294 // 541. shared_ptr template assignment and void
299 typedef void element_type
;
300 } _GLIBCXX11_DEPRECATED
;
302 #if __cplusplus >= 201103L
304 template<_Lock_policy _Lp
>
305 template<typename _Tp
>
307 __shared_count
<_Lp
>::__shared_count(std::auto_ptr
<_Tp
>&& __r
)
308 : _M_pi(new _Sp_counted_ptr
<_Tp
*, _Lp
>(__r
.get()))
311 template<typename _Tp
, _Lock_policy _Lp
>
312 template<typename _Tp1
, typename
>
314 __shared_ptr
<_Tp
, _Lp
>::__shared_ptr(std::auto_ptr
<_Tp1
>&& __r
)
315 : _M_ptr(__r
.get()), _M_refcount()
317 __glibcxx_function_requires(_ConvertibleConcept
<_Tp1
*, _Tp
*>)
318 static_assert( sizeof(_Tp1
) > 0, "incomplete type" );
319 _Tp1
* __tmp
= __r
.get();
320 _M_refcount
= __shared_count
<_Lp
>(std::move(__r
));
321 _M_enable_shared_from_this_with(__tmp
);
324 template<typename _Tp
>
325 template<typename _Tp1
, typename
>
327 shared_ptr
<_Tp
>::shared_ptr(std::auto_ptr
<_Tp1
>&& __r
)
328 : __shared_ptr
<_Tp
>(std::move(__r
)) { }
331 template<typename _Tp
, typename _Dp
>
332 template<typename _Up
, typename
>
334 unique_ptr
<_Tp
, _Dp
>::unique_ptr(auto_ptr
<_Up
>&& __u
) noexcept
335 : _M_t(__u
.release(), deleter_type()) { }
338 #pragma GCC diagnostic pop
340 _GLIBCXX_END_NAMESPACE_VERSION
343 #endif /* _BACKWARD_AUTO_PTR_H */