.TH "std::weak_ptr< _Tp >" 3cxx "Thu Feb 16 2023" "libstdc++" \" -*- nroff -*-
.ad l
.nh
.SH NAME
std::weak_ptr< _Tp > \- A non-owning observer for a pointer owned by a shared_ptr\&.  

.SH SYNOPSIS
.br
.PP
.PP
\fC#include <shared_ptr\&.h>\fP
.PP
Inherits std::__weak_ptr< _Tp, _Lp >\&.
.SS "Public Types"

.in +1c
.ti -1c
.RI "using \fBelement_type\fP = typename \fBremove_extent\fP< _Tp >::type"
.br
.in -1c
.SS "Public Member Functions"

.in +1c
.ti -1c
.RI "template<typename _Yp , typename  = _Constructible<const shared_ptr<_Yp>&>> \fBweak_ptr\fP (const \fBshared_ptr\fP< _Yp > &__r) noexcept"
.br
.ti -1c
.RI "\fBweak_ptr\fP (const \fBweak_ptr\fP &) noexcept=default"
.br
.ti -1c
.RI "template<typename _Yp , typename  = _Constructible<const weak_ptr<_Yp>&>> \fBweak_ptr\fP (const \fBweak_ptr\fP< _Yp > &__r) noexcept"
.br
.ti -1c
.RI "\fBweak_ptr\fP (\fBweak_ptr\fP &&) noexcept=default"
.br
.ti -1c
.RI "template<typename _Yp , typename  = _Constructible<weak_ptr<_Yp>>> \fBweak_ptr\fP (\fBweak_ptr\fP< _Yp > &&__r) noexcept"
.br
.ti -1c
.RI "bool \fBexpired\fP () const noexcept"
.br
.ti -1c
.RI "\fBshared_ptr\fP< _Tp > \fBlock\fP () const noexcept"
.br
.ti -1c
.RI "template<typename _Yp > _Assignable< const \fBshared_ptr\fP< _Yp > & > \fBoperator=\fP (const \fBshared_ptr\fP< _Yp > &__r) noexcept"
.br
.ti -1c
.RI "\fBweak_ptr\fP & \fBoperator=\fP (const \fBweak_ptr\fP &__r) noexcept=default"
.br
.ti -1c
.RI "template<typename _Yp > _Assignable< const \fBweak_ptr\fP< _Yp > & > \fBoperator=\fP (const \fBweak_ptr\fP< _Yp > &__r) noexcept"
.br
.ti -1c
.RI "\fBweak_ptr\fP & \fBoperator=\fP (\fBweak_ptr\fP &&__r) noexcept=default"
.br
.ti -1c
.RI "template<typename _Yp > _Assignable< \fBweak_ptr\fP< _Yp > > \fBoperator=\fP (\fBweak_ptr\fP< _Yp > &&__r) noexcept"
.br
.ti -1c
.RI "template<typename _Tp1 > bool \fBowner_before\fP (const __shared_ptr< _Tp1, _Lp > &__rhs) const noexcept"
.br
.ti -1c
.RI "template<typename _Tp1 > bool \fBowner_before\fP (const __weak_ptr< _Tp1, _Lp > &__rhs) const noexcept"
.br
.ti -1c
.RI "void \fBreset\fP () noexcept"
.br
.ti -1c
.RI "void \fBswap\fP (__weak_ptr &__s) noexcept"
.br
.ti -1c
.RI "long \fBuse_count\fP () const noexcept"
.br
.in -1c
.SS "Related Functions"
(Note that these are not member functions\&.) 
.in +1c
.ti -1c
.RI "template<typename _Tp > void \fBswap\fP (\fBweak_ptr\fP< _Tp > &__a, \fBweak_ptr\fP< _Tp > &__b) noexcept"
.br
.RI "Swap overload for weak_ptr\&. "
.in -1c
.SH "Detailed Description"
.PP 

.SS "template<typename _Tp>
.br
class std::weak_ptr< _Tp >"A non-owning observer for a pointer owned by a shared_ptr\&. 

A weak_ptr provides a safe alternative to a raw pointer when you want a non-owning reference to an object that is managed by a shared_ptr\&.
.PP
Unlike a raw pointer, a weak_ptr can be converted to a new shared_ptr that shares ownership with every other shared_ptr that already owns the pointer\&. In other words you can upgrade from a non-owning 'weak' reference to an owning shared_ptr, without having access to any of the existing shared_ptr objects\&.
.PP
Also unlike a raw pointer, a weak_ptr does not become 'dangling' after the object it points to has been destroyed\&. Instead, a weak_ptr becomes \fIexpired\fP and can no longer be converted to a shared_ptr that owns the freed pointer, so you cannot accidentally access the pointed-to object after it has been destroyed\&. 
.PP
Definition at line \fB686\fP of file \fBbits/shared_ptr\&.h\fP\&.
.SH "Member Typedef Documentation"
.PP 
.SS "template<typename _Tp , _Lock_policy _Lp> using std::__weak_ptr< _Tp, _Lp >::element_type =  typename \fBremove_extent\fP<_Tp>::type\fC [inherited]\fP"

.PP
Definition at line \fB1602\fP of file \fBshared_ptr_base\&.h\fP\&.
.SH "Constructor & Destructor Documentation"
.PP 
.SS "template<typename _Tp > template<typename _Yp , typename  = _Constructible<const shared_ptr<_Yp>&>> \fBstd::weak_ptr\fP< _Tp >::weak_ptr (const \fBshared_ptr\fP< _Yp > & __r)\fC [inline]\fP, \fC [noexcept]\fP"

.PP
Definition at line \fB703\fP of file \fBbits/shared_ptr\&.h\fP\&.
.SS "template<typename _Tp > template<typename _Yp , typename  = _Constructible<const weak_ptr<_Yp>&>> \fBstd::weak_ptr\fP< _Tp >::weak_ptr (const \fBweak_ptr\fP< _Yp > & __r)\fC [inline]\fP, \fC [noexcept]\fP"

.PP
Definition at line \fB709\fP of file \fBbits/shared_ptr\&.h\fP\&.
.SS "template<typename _Tp > template<typename _Yp , typename  = _Constructible<weak_ptr<_Yp>>> \fBstd::weak_ptr\fP< _Tp >::weak_ptr (\fBweak_ptr\fP< _Yp > && __r)\fC [inline]\fP, \fC [noexcept]\fP"

.PP
Definition at line \fB715\fP of file \fBbits/shared_ptr\&.h\fP\&.
.SH "Member Function Documentation"
.PP 
.SS "template<typename _Tp , _Lock_policy _Lp> bool std::__weak_ptr< _Tp, _Lp >::expired () const\fC [inline]\fP, \fC [noexcept]\fP, \fC [inherited]\fP"

.PP
Definition at line \fB1694\fP of file \fBshared_ptr_base\&.h\fP\&.
.SS "template<typename _Tp > \fBshared_ptr\fP< _Tp > \fBstd::weak_ptr\fP< _Tp >::lock () const\fC [inline]\fP, \fC [noexcept]\fP"

.PP
Definition at line \fB749\fP of file \fBbits/shared_ptr\&.h\fP\&.
.SS "template<typename _Tp > template<typename _Yp > _Assignable< const \fBshared_ptr\fP< _Yp > & > \fBstd::weak_ptr\fP< _Tp >::operator= (const \fBshared_ptr\fP< _Yp > & __r)\fC [inline]\fP, \fC [noexcept]\fP"

.PP
Definition at line \fB731\fP of file \fBbits/shared_ptr\&.h\fP\&.
.SS "template<typename _Tp > template<typename _Yp > _Assignable< const \fBweak_ptr\fP< _Yp > & > \fBstd::weak_ptr\fP< _Tp >::operator= (const \fBweak_ptr\fP< _Yp > & __r)\fC [inline]\fP, \fC [noexcept]\fP"

.PP
Definition at line \fB723\fP of file \fBbits/shared_ptr\&.h\fP\&.
.SS "template<typename _Tp > template<typename _Yp > _Assignable< \fBweak_ptr\fP< _Yp > > \fBstd::weak_ptr\fP< _Tp >::operator= (\fBweak_ptr\fP< _Yp > && __r)\fC [inline]\fP, \fC [noexcept]\fP"

.PP
Definition at line \fB742\fP of file \fBbits/shared_ptr\&.h\fP\&.
.SS "template<typename _Tp , _Lock_policy _Lp> template<typename _Tp1 > bool std::__weak_ptr< _Tp, _Lp >::owner_before (const __shared_ptr< _Tp1, _Lp > & __rhs) const\fC [inline]\fP, \fC [noexcept]\fP, \fC [inherited]\fP"

.PP
Definition at line \fB1699\fP of file \fBshared_ptr_base\&.h\fP\&.
.SS "template<typename _Tp , _Lock_policy _Lp> template<typename _Tp1 > bool std::__weak_ptr< _Tp, _Lp >::owner_before (const __weak_ptr< _Tp1, _Lp > & __rhs) const\fC [inline]\fP, \fC [noexcept]\fP, \fC [inherited]\fP"

.PP
Definition at line \fB1704\fP of file \fBshared_ptr_base\&.h\fP\&.
.SS "template<typename _Tp , _Lock_policy _Lp> void std::__weak_ptr< _Tp, _Lp >::reset ()\fC [inline]\fP, \fC [noexcept]\fP, \fC [inherited]\fP"

.PP
Definition at line \fB1708\fP of file \fBshared_ptr_base\&.h\fP\&.
.SS "template<typename _Tp , _Lock_policy _Lp> void std::__weak_ptr< _Tp, _Lp >::swap (__weak_ptr< _Tp, _Lp > & __s)\fC [inline]\fP, \fC [noexcept]\fP, \fC [inherited]\fP"

.PP
Definition at line \fB1712\fP of file \fBshared_ptr_base\&.h\fP\&.
.SS "template<typename _Tp , _Lock_policy _Lp> long std::__weak_ptr< _Tp, _Lp >::use_count () const\fC [inline]\fP, \fC [noexcept]\fP, \fC [inherited]\fP"

.PP
Definition at line \fB1690\fP of file \fBshared_ptr_base\&.h\fP\&.

.SH "Author"
.PP 
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