std::shared_ptr< _Tp >(3cxx)

NAME
std::shared_ptr< _Tp > - A smart pointer with reference-counted copy semantics.

SYNOPSIS

Inherits std::__shared_ptr< _Tp, _Lp >.

  Public Types

using element_type = typename __shared_ptr< _Tp >::element_type
The type pointed to by the stored pointer, remove_extent_t<_Tp>
using weak_type = weak_ptr< _Tp >
The corresponding weak_ptr type for this shared_ptr.

  Public Member Functions

constexpr shared_ptr () noexcept
Construct an empty shared_ptr.
template<typename _Yp , typename = _Constructible<_Yp*>> shared_ptr (_Yp *__p)
Construct a shared_ptr that owns the pointer __p.
template<typename _Yp , typename _Deleter , typename = _Constructible<_Yp*, _Deleter>> shared_ptr (_Yp *__p, _Deleter __d)
Construct a shared_ptr that owns the pointer __p and the deleter __d.
template<typename _Yp , typename _Deleter , typename _Alloc , typename = _Constructible<_Yp*, _Deleter, _Alloc>> shared_ptr (_Yp *__p, _Deleter __d, _Alloc __a)
Construct a shared_ptr that owns the pointer __p and the deleter __d.
shared_ptr (const shared_ptr &) noexcept=default
Copy constructor.
template<typename _Yp , typename = _Constructible<const shared_ptr<_Yp>&>> shared_ptr (const shared_ptr< _Yp > &__r) noexcept
If __r is empty, constructs an empty shared_ptr; otherwise construct a shared_ptr that shares ownership with __r.
template<typename _Yp > shared_ptr (const shared_ptr< _Yp > &__r, element_type *__p) noexcept
Constructs a shared_ptr instance that stores __p and shares ownership with __r.
template<typename _Yp , typename = _Constructible<const weak_ptr<_Yp>&>> shared_ptr (const weak_ptr< _Yp > &__r)
Constructs a shared_ptr that shares ownership with __r and stores a copy of the pointer stored in __r.
template<typename _Deleter > shared_ptr (nullptr_t __p, _Deleter __d)
Construct a shared_ptr that owns a null pointer and the deleter __d.
template<typename _Deleter , typename _Alloc > shared_ptr (nullptr_t __p, _Deleter __d, _Alloc __a)
Construct a shared_ptr that owns a null pointer and the deleter __d.
constexpr shared_ptr (nullptr_t) noexcept
Construct an empty shared_ptr.
shared_ptr (shared_ptr &&__r) noexcept
Move-constructs a shared_ptr instance from __r.
template<typename _Yp , typename = _Constructible<shared_ptr<_Yp>>> shared_ptr (shared_ptr< _Yp > &&__r) noexcept
Move-constructs a shared_ptr instance from __r.
template<typename _Tp1 , typename > shared_ptr (std::auto_ptr< _Tp1 > &&__r)
template<typename _Yp , typename _Del , typename = _Constructible<unique_ptr<_Yp, _Del>>> shared_ptr (unique_ptr< _Yp, _Del > &&__r)
element_type * get () const noexcept
Return the stored pointer.
operator bool () const noexcept
Return true if the stored pointer is not null.
element_type & operator* () const noexcept
element_type * operator-> () const noexcept
shared_ptr & operator= (const shared_ptr &) noexcept=default
template<typename _Yp > _Assignable< const shared_ptr< _Yp > & > operator= (const shared_ptr< _Yp > &__r) noexcept
shared_ptr & operator= (shared_ptr &&__r) noexcept
template<class _Yp > _Assignable< shared_ptr< _Yp > > operator= (shared_ptr< _Yp > &&__r) noexcept
template<typename _Yp , typename _Del > _Assignable< unique_ptr< _Yp, _Del > > operator= (unique_ptr< _Yp, _Del > &&__r)
void reset () noexcept
template<typename _Yp > _SafeConv< _Yp > reset (_Yp *__p)
template<typename _Yp , typename _Deleter > _SafeConv< _Yp > reset (_Yp *__p, _Deleter __d)
template<typename _Yp , typename _Deleter , typename _Alloc > _SafeConv< _Yp > reset (_Yp *__p, _Deleter __d, _Alloc __a)
void swap (__shared_ptr< _Tp, _Lp > &__other) noexcept
Exchange both the owned pointer and the stored pointer.
bool unique () const noexcept
Return true if use_count() == 1.
long use_count () const noexcept
If *this owns a pointer, return the number of owners, otherwise zero.

template<typename _Tp1 > bool owner_before (__shared_ptr< _Tp1, _Lp > const &__rhs) const noexcept
Define an ordering based on ownership.
template<typename _Tp1 > bool owner_before (__weak_ptr< _Tp1, _Lp > const &__rhs) const noexcept
Define an ordering based on ownership.

  Friends

template<typename _Yp , typename _Alloc , typename... _Args> shared_ptr< _Yp > allocate_shared (const _Alloc &__a, _Args &&... __args)
class weak_ptr< _Tp >

  Related Functions
(Note that these are not member functions.)
template<typename _Del , typename _Tp > _Del * get_deleter (const shared_ptr< _Tp > &__p) noexcept
20.7.2.2.10 shared_ptr get_deleter
template<typename _Ch , typename _Tr , typename _Tp , _Lock_policy _Lp> std::basic_ostream< _Ch, _Tr > & operator<< (std::basic_ostream< _Ch, _Tr > &__os, const __shared_ptr< _Tp, _Lp > &__p)
Write the stored pointer to an ostream.

template<typename _Tp , typename _Up > bool operator== (const shared_ptr< _Tp > &__a, const shared_ptr< _Up > &__b) noexcept
template<typename _Tp > bool operator== (const shared_ptr< _Tp > &__a, nullptr_t) noexcept
shared_ptr comparison with nullptr
template<typename _Tp > bool operator== (nullptr_t, const shared_ptr< _Tp > &__a) noexcept
shared_ptr comparison with nullptr
template<typename _Tp , typename _Up > bool operator!= (const shared_ptr< _Tp > &__a, const shared_ptr< _Up > &__b) noexcept
Inequality operator for shared_ptr objects, compares the stored pointers.
template<typename _Tp > bool operator!= (const shared_ptr< _Tp > &__a, nullptr_t) noexcept
shared_ptr comparison with nullptr
template<typename _Tp > bool operator!= (nullptr_t, const shared_ptr< _Tp > &__a) noexcept
shared_ptr comparison with nullptr
template<typename _Tp , typename _Up > bool operator< (const shared_ptr< _Tp > &__a, const shared_ptr< _Up > &__b) noexcept
Relational operator for shared_ptr objects, compares the stored pointers.
template<typename _Tp > bool operator< (const shared_ptr< _Tp > &__a, nullptr_t) noexcept
shared_ptr comparison with nullptr
template<typename _Tp > bool operator< (nullptr_t, const shared_ptr< _Tp > &__a) noexcept
shared_ptr comparison with nullptr
template<typename _Tp , typename _Up > bool operator<= (const shared_ptr< _Tp > &__a, const shared_ptr< _Up > &__b) noexcept
Relational operator for shared_ptr objects, compares the stored pointers.
template<typename _Tp > bool operator<= (const shared_ptr< _Tp > &__a, nullptr_t) noexcept
shared_ptr comparison with nullptr
template<typename _Tp > bool operator<= (nullptr_t, const shared_ptr< _Tp > &__a) noexcept
shared_ptr comparison with nullptr
template<typename _Tp , typename _Up > bool operator> (const shared_ptr< _Tp > &__a, const shared_ptr< _Up > &__b) noexcept
Relational operator for shared_ptr objects, compares the stored pointers.
template<typename _Tp > bool operator> (const shared_ptr< _Tp > &__a, nullptr_t) noexcept
shared_ptr comparison with nullptr
template<typename _Tp > bool operator> (nullptr_t, const shared_ptr< _Tp > &__a) noexcept
shared_ptr comparison with nullptr
template<typename _Tp , typename _Up > bool operator>= (const shared_ptr< _Tp > &__a, const shared_ptr< _Up > &__b) noexcept
Relational operator for shared_ptr objects, compares the stored pointers.
template<typename _Tp > bool operator>= (const shared_ptr< _Tp > &__a, nullptr_t) noexcept
shared_ptr comparison with nullptr
template<typename _Tp > bool operator>= (nullptr_t, const shared_ptr< _Tp > &__a) noexcept
shared_ptr comparison with nullptr
template<typename _Tp > void swap (shared_ptr< _Tp > &__a, shared_ptr< _Tp > &__b) noexcept
Swap overload for shared_ptr.
template<typename _Tp , typename _Up > shared_ptr< _Tp > static_pointer_cast (const shared_ptr< _Up > &__r) noexcept
Convert type of shared_ptr, via static_cast
template<typename _Tp , typename _Up > shared_ptr< _Tp > const_pointer_cast (const shared_ptr< _Up > &__r) noexcept
Convert type of shared_ptr, via const_cast
template<typename _Tp , typename _Up > shared_ptr< _Tp > dynamic_pointer_cast (const shared_ptr< _Up > &__r) noexcept
Convert type of shared_ptr, via dynamic_cast
template<typename _Tp , typename _Up > shared_ptr< _Tp > reinterpret_pointer_cast (const shared_ptr< _Up > &__r) noexcept
Convert type of shared_ptr, via reinterpret_cast

template<typename _Tp , typename _Alloc , typename... _Args> shared_ptr< _Tp > allocate_shared (const _Alloc &__a, _Args &&... __args)
Create an object that is owned by a shared_ptr.
template<typename _Tp , typename... _Args> shared_ptr< _Tp > make_shared (_Args &&... __args)
Create an object that is owned by a shared_ptr.

template<typename _Tp , _Lock_policy _Lp> bool atomic_is_lock_free (const __shared_ptr< _Tp, _Lp > *__p)
Report whether shared_ptr atomic operations are lock-free.

template<typename _Tp > shared_ptr< _Tp > atomic_load_explicit (const shared_ptr< _Tp > *__p, memory_order)
Atomic load for shared_ptr objects.

template<typename _Tp > void atomic_store_explicit (shared_ptr< _Tp > *__p, shared_ptr< _Tp > __r, memory_order)
Atomic store for shared_ptr objects.

template<typename _Tp > shared_ptr< _Tp > atomic_exchange_explicit (shared_ptr< _Tp > *__p, shared_ptr< _Tp > __r, memory_order)
Atomic exchange for shared_ptr objects.

template<typename _Tp > bool atomic_compare_exchange_strong_explicit (shared_ptr< _Tp > *__p, shared_ptr< _Tp > *__v, shared_ptr< _Tp > __w, memory_order, memory_order)
Atomic compare-and-swap for shared_ptr objects.

Detailed Description

  template<typename _Tp>
class std::shared_ptr< _Tp >" A smart pointer with reference-counted copy semantics.

A shared_ptr object is either empty or owns a pointer passed to the constructor. Copies of a shared_ptr share ownership of the same pointer. When the last shared_ptr that owns the pointer is destroyed or reset, the owned pointer is freed (either by delete or by invoking a custom deleter that was passed to the constructor).

A shared_ptr also stores another pointer, which is usually (but not always) the same pointer as it owns. The stored pointer can be retrieved by calling the get() member function.

The equality and relational operators for shared_ptr only compare the stored pointer returned by get(), not the owned pointer. To test whether two shared_ptr objects share ownership of the same pointer see std::shared_ptr::owner_before and std::owner_less.

Definition at line 122 of file bits/shared_ptr.h.

Member Typedef Documentation

  template<typename _Tp > using std::shared_ptr< _Tp >::element_type = typename __shared_ptr<_Tp>::element_type

The type pointed to by the stored pointer, remove_extent_t<_Tp>

Definition at line 137 of file bits/shared_ptr.h.

  template<typename _Tp > using std::shared_ptr< _Tp >::weak_type = weak_ptr<_Tp>

The corresponding weak_ptr type for this shared_ptr.

Definition at line 142 of file bits/shared_ptr.h.

Constructor & Destructor Documentation

  template<typename _Tp > constexpr std::shared_ptr< _Tp >::shared_ptr () [inline], [constexpr], [noexcept]

Construct an empty shared_ptr.

Postcondition
    use_count()==0 && get()==0

Definition at line 148 of file bits/shared_ptr.h.

  template<typename _Tp > std::shared_ptr< _Tp >::shared_ptr (const shared_ptr< _Tp > &) [default], [noexcept]

Copy constructor.

  template<typename _Tp > template<typename _Yp , typename = _Constructible<_Yp*>> std::shared_ptr< _Tp >::shared_ptr (_Yp * __p) [inline], [explicit]

Construct a shared_ptr that owns the pointer __p.

Parameters
    __p A pointer that is convertible to element_type*.

Postcondition
    use_count() == 1 && get() == __p

Exceptions
    std::bad_alloc,in which case delete __p is called.

Definition at line 160 of file bits/shared_ptr.h.

  template<typename _Tp > template<typename _Yp , typename _Deleter , typename = _Constructible<_Yp*, _Deleter>> std::shared_ptr< _Tp >::shared_ptr (_Yp * __p, _Deleter __d) [inline]

Construct a shared_ptr that owns the pointer __p and the deleter __d.

Parameters
    __p A pointer.
    __d A deleter.

Postcondition
    use_count() == 1 && get() == __p

Exceptions
    std::bad_alloc,in which case __d(__p) is called.

Requirements: _Deleter's copy constructor and destructor must not throw

__shared_ptr will release __p by calling __d(__p)

Definition at line 177 of file bits/shared_ptr.h.

  template<typename _Tp > template<typename _Deleter > std::shared_ptr< _Tp >::shared_ptr (nullptr_t __p, _Deleter __d) [inline]

Construct a shared_ptr that owns a null pointer and the deleter __d.

Parameters
    __p A null pointer constant.
    __d A deleter.

Postcondition
    use_count() == 1 && get() == __p

Exceptions
    std::bad_alloc,in which case __d(__p) is called.

Requirements: _Deleter's copy constructor and destructor must not throw

The last owner will call __d(__p)

Definition at line 194 of file bits/shared_ptr.h.

  template<typename _Tp > template<typename _Yp , typename _Deleter , typename _Alloc , typename = _Constructible<_Yp*, _Deleter, _Alloc>> std::shared_ptr< _Tp >::shared_ptr (_Yp * __p, _Deleter __d, _Alloc __a) [inline]

Construct a shared_ptr that owns the pointer __p and the deleter __d.

Parameters
    __p A pointer.
    __d A deleter.
    __a An allocator.

Postcondition
    use_count() == 1 && get() == __p

Exceptions
    std::bad_alloc,in which case __d(__p) is called.

Requirements: _Deleter's copy constructor and destructor must not throw _Alloc's copy constructor and destructor must not throw.

__shared_ptr will release __p by calling __d(__p)

Definition at line 214 of file bits/shared_ptr.h.

  template<typename _Tp > template<typename _Deleter , typename _Alloc > std::shared_ptr< _Tp >::shared_ptr (nullptr_t __p, _Deleter __d, _Alloc __a) [inline]

Construct a shared_ptr that owns a null pointer and the deleter __d.

Parameters
    __p A null pointer constant.
    __d A deleter.
    __a An allocator.

Postcondition
    use_count() == 1 && get() == __p

Exceptions
    std::bad_alloc,in which case __d(__p) is called.

Requirements: _Deleter's copy constructor and destructor must not throw _Alloc's copy constructor and destructor must not throw.

The last owner will call __d(__p)

Definition at line 233 of file bits/shared_ptr.h.

  template<typename _Tp > template<typename _Yp > std::shared_ptr< _Tp >::shared_ptr (const shared_ptr< _Yp > & __r, element_type * __p) [inline], [noexcept]

Constructs a shared_ptr instance that stores __p and shares ownership with __r.

Parameters
    __r A shared_ptr.
    __p A pointer that will remain valid while *__r is valid.

Postcondition
    get() == __p && use_count() == __r.use_count()

This can be used to construct a shared_ptr to a sub-object of an object managed by an existing shared_ptr. The complete object will remain valid while any shared_ptr owns it, even if they don't store a pointer to the complete object.

shared_ptr<pair<int,int>> pii(new pair<int,int>());
shared_ptr<int> pi(pii, &pii->first);
assert(pii.use_count() == 2);

Definition at line 257 of file bits/shared_ptr.h.

  template<typename _Tp > template<typename _Yp , typename = _Constructible<const shared_ptr<_Yp>&>> std::shared_ptr< _Tp >::shared_ptr (const shared_ptr< _Yp > & __r) [inline], [noexcept]

If __r is empty, constructs an empty shared_ptr; otherwise construct a shared_ptr that shares ownership with __r.

Parameters
    __r A shared_ptr.

Postcondition
    get() == __r.get() && use_count() == __r.use_count()

Definition at line 296 of file bits/shared_ptr.h.

  template<typename _Tp > std::shared_ptr< _Tp >::shared_ptr (shared_ptr< _Tp > && __r) [inline], [noexcept]

Move-constructs a shared_ptr instance from __r.

Parameters
    __r A shared_ptr rvalue.

Postcondition
    *this contains the old value of __r, __r is empty.

Definition at line 304 of file bits/shared_ptr.h.

  template<typename _Tp > template<typename _Yp , typename = _Constructible<shared_ptr<_Yp>>> std::shared_ptr< _Tp >::shared_ptr (shared_ptr< _Yp > && __r) [inline], [noexcept]

Move-constructs a shared_ptr instance from __r.

Parameters
    __r A shared_ptr rvalue.

Postcondition
    *this contains the old value of __r, __r is empty.

Definition at line 313 of file bits/shared_ptr.h.

  template<typename _Tp > template<typename _Yp , typename = _Constructible<const weak_ptr<_Yp>&>> std::shared_ptr< _Tp >::shared_ptr (const weak_ptr< _Yp > & __r) [inline], [explicit]

Constructs a shared_ptr that shares ownership with __r and stores a copy of the pointer stored in __r.

Parameters
    __r A weak_ptr.

Postcondition
    use_count() == __r.use_count()

Exceptions
    bad_weak_ptr when __r.expired(), in which case the constructor has no effect.

Definition at line 325 of file bits/shared_ptr.h.

  template<typename _Tp > constexpr std::shared_ptr< _Tp >::shared_ptr (nullptr_t) [inline], [constexpr], [noexcept]

Construct an empty shared_ptr.

Postcondition
    use_count() == 0 && get() == nullptr

Definition at line 357 of file bits/shared_ptr.h.

Member Function Documentation

  template<typename _Tp , _Lock_policy _Lp> element_type* std::__shared_ptr< _Tp, _Lp >::get (void) const [inline], [noexcept], [inherited]

Return the stored pointer.

Definition at line 1295 of file shared_ptr_base.h.

  template<typename _Tp , _Lock_policy _Lp> std::__shared_ptr< _Tp, _Lp >::operator bool () const [inline], [explicit], [noexcept], [inherited]

Return true if the stored pointer is not null.

Definition at line 1299 of file shared_ptr_base.h.

  template<typename _Tp , _Lock_policy _Lp> template<typename _Tp1 > bool std::__shared_ptr< _Tp, _Lp >::owner_before (__shared_ptr< _Tp1, _Lp > const & __rhs) const [inline], [noexcept], [inherited]

Define an ordering based on ownership. This function defines a strict weak ordering between two shared_ptr or weak_ptr objects, such that one object is less than the other unless they share ownership of the same pointer, or are both empty.

Definition at line 1329 of file shared_ptr_base.h.

  template<typename _Tp , _Lock_policy _Lp> template<typename _Tp1 > bool std::__shared_ptr< _Tp, _Lp >::owner_before (__weak_ptr< _Tp1, _Lp > const & __rhs) const [inline], [noexcept], [inherited]

Define an ordering based on ownership. This function defines a strict weak ordering between two shared_ptr or weak_ptr objects, such that one object is less than the other unless they share ownership of the same pointer, or are both empty.

Definition at line 1334 of file shared_ptr_base.h.

  template<typename _Tp , _Lock_policy _Lp> void std::__shared_ptr< _Tp, _Lp >::swap (__shared_ptr< _Tp, _Lp > & __other) [inline], [noexcept], [inherited]

Exchange both the owned pointer and the stored pointer.

Definition at line 1314 of file shared_ptr_base.h.

  template<typename _Tp , _Lock_policy _Lp> bool std::__shared_ptr< _Tp, _Lp >::unique () const [inline], [noexcept], [inherited]

Return true if use_count() == 1.

Definition at line 1304 of file shared_ptr_base.h.

  template<typename _Tp , _Lock_policy _Lp> long std::__shared_ptr< _Tp, _Lp >::use_count () const [inline], [noexcept], [inherited]

If *this owns a pointer, return the number of owners, otherwise zero.

Definition at line 1309 of file shared_ptr_base.h.

Author

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