oracular (3) std::shared_ptr.3cxx.gz
NAME
std::shared_ptr< _Tp > - A smart pointer with reference-counted copy semantics.
SYNOPSIS
#include <memory>
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.
template<typename _Yp , typename = _Constructible<auto_ptr<_Yp>>> shared_ptr (auto_ptr< _Yp > &&__r)
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 _Yp > shared_ptr (shared_ptr< _Yp > &&__r, element_type *__p) noexcept
Constructs a shared_ptr instance that stores __p and shares ownership with __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
template<typename _Yp > _Assignable< auto_ptr< _Yp > > operator= (auto_ptr< _Yp > &&__r)
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 > shared_ptr< _BoundedArray< _Yp > > allocate_shared (const
_Alloc &)
template<typename _Yp , typename _Alloc , typename... _Args> shared_ptr< _NonArray< _Yp > >
allocate_shared (const _Alloc &, _Args &&...)
template<typename _Yp , typename _Alloc > shared_ptr< _BoundedArray< _Yp > > allocate_shared (const
_Alloc &, const remove_extent_t< _Yp > &)
template<typename _Yp , typename _Alloc > shared_ptr< _UnboundedArray< _Yp > > allocate_shared (const
_Alloc &, size_t)
template<typename _Yp , typename _Alloc > shared_ptr< _UnboundedArray< _Yp > > allocate_shared (const
_Alloc &, size_t, const remove_extent_t< _Yp > &)
template<typename _Yp , typename _Alloc > shared_ptr< _NotUnboundedArray< _Yp > >
allocate_shared_for_overwrite (const _Alloc &)
template<typename _Yp , typename _Alloc > shared_ptr< _UnboundedArray< _Yp > >
allocate_shared_for_overwrite (const _Alloc &, size_t)
template<typename _Yp > shared_ptr< _BoundedArray< _Yp > > make_shared ()
template<typename _Yp , typename... _Args> shared_ptr< _NonArray< _Yp > > make_shared (_Args &&...)
template<typename _Yp > shared_ptr< _BoundedArray< _Yp > > make_shared (const remove_extent_t< _Yp > &)
template<typename _Yp > shared_ptr< _UnboundedArray< _Yp > > make_shared (size_t)
template<typename _Yp > shared_ptr< _UnboundedArray< _Yp > > make_shared (size_t, const remove_extent_t<
_Yp > &)
template<typename _Yp > shared_ptr< _NotUnboundedArray< _Yp > > make_shared_for_overwrite ()
template<typename _Yp > shared_ptr< _UnboundedArray< _Yp > > make_shared_for_overwrite (size_t)
class weak_ptr< _Tp >
Related Symbols
(Note that these are not member symbols.)
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 > 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 _Up > shared_ptr< _Tp > static_pointer_cast (shared_ptr< _Up >
&&__r) noexcept
Convert type of shared_ptr rvalue, via static_cast
template<typename _Tp , typename _Up > shared_ptr< _Tp > const_pointer_cast (shared_ptr< _Up > &&__r)
noexcept
Convert type of shared_ptr rvalue, via const_cast
template<typename _Tp , typename _Up > shared_ptr< _Tp > dynamic_pointer_cast (shared_ptr< _Up >
&&__r) noexcept
Convert type of shared_ptr rvalue, via dynamic_cast
template<typename _Tp , typename _Up > shared_ptr< _Tp > reinterpret_pointer_cast (shared_ptr< _Up >
&&__r) noexcept
Convert type of shared_ptr rvalue, via reinterpret_cast
template<typename _Tp , typename _Alloc , typename... _Args> shared_ptr< _NonArray< _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< _NonArray< _Tp > > make_shared (_Args &&...
__args)
Create an object that is owned by a shared_ptr.
template<typename _Tp , typename _Alloc > shared_ptr< _UnboundedArray< _Tp > > allocate_shared (const
_Alloc &__a, size_t __n)
Create an object that is owned by a shared_ptr.
template<typename _Tp , typename _Alloc > shared_ptr< _BoundedArray< _Tp > > allocate_shared (const
_Alloc &__a)
Create an object that is owned by a shared_ptr.
Detailed Description
template<typename _Tp>
class std::shared_ptr< _Tp >"A smart pointer with reference-counted copy semantics.
Since
C++11
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.
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>
template<typename _Tp > using std::shared_ptr< _Tp >::weak_type = weak_ptr<_Tp>
The corresponding weak_ptr type for this shared_ptr.
Since
C++17
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
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.
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)
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)
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)
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)
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);
template<typename _Tp > template<typename _Yp > std::shared_ptr< _Tp >::shared_ptr (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 && !__r.use_count() && !__r.get()
Since
C++17
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> pi1(pii, &pii->first);
assert(pii.use_count() == 2);
shared_ptr<int> pi2(std::move(pii), &pii->second);
assert(pii.use_count() == 0);
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()
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.
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.
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.
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
Member Function Documentation
template<typename _Tp , _Lock_policy _Lp> element_type * std::__shared_ptr< _Tp, _Lp >::get () const
[inline], [noexcept], [inherited]
Return the stored pointer.
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.
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.
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.
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.
template<typename _Tp , _Lock_policy _Lp> bool std::__shared_ptr< _Tp, _Lp >::unique () const [inline],
[noexcept], [inherited]
Return true if use_count() == 1.
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.
Author
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