.TH "std::weak_ptr< _Tp >" 3cxx "Tue Jul 18 2023" "libstdc++" \" -*- nroff -*-
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.SH NAME
std::weak_ptr< _Tp > \- A non-owning observer for a pointer owned by a shared_ptr\&.  

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

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

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.ti -1c
.RI "template<typename _Yp , typename  = _Constructible<const shared_ptr<_Yp>&>> \fBweak_ptr\fP (const \fBshared_ptr\fP< _Yp > &__r) noexcept"
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.ti -1c
.RI "\fBweak_ptr\fP (const \fBweak_ptr\fP &) noexcept=default"
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.RI "template<typename _Yp , typename  = _Constructible<const weak_ptr<_Yp>&>> \fBweak_ptr\fP (const \fBweak_ptr\fP< _Yp > &__r) noexcept"
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.ti -1c
.RI "\fBweak_ptr\fP (\fBweak_ptr\fP &&) noexcept=default"
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.ti -1c
.RI "template<typename _Yp , typename  = _Constructible<weak_ptr<_Yp>>> \fBweak_ptr\fP (\fBweak_ptr\fP< _Yp > &&__r) noexcept"
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.ti -1c
.RI "bool \fBexpired\fP () const noexcept"
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.ti -1c
.RI "\fBshared_ptr\fP< _Tp > \fBlock\fP () const noexcept"
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.ti -1c
.RI "template<typename _Yp > _Assignable< const \fBshared_ptr\fP< _Yp > & > \fBoperator=\fP (const \fBshared_ptr\fP< _Yp > &__r) noexcept"
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.RI "\fBweak_ptr\fP & \fBoperator=\fP (const \fBweak_ptr\fP &__r) noexcept=default"
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.ti -1c
.RI "template<typename _Yp > _Assignable< const \fBweak_ptr\fP< _Yp > & > \fBoperator=\fP (const \fBweak_ptr\fP< _Yp > &__r) noexcept"
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.ti -1c
.RI "\fBweak_ptr\fP & \fBoperator=\fP (\fBweak_ptr\fP &&__r) noexcept=default"
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.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"
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.ti -1c
.RI "template<typename _Tp1 > bool \fBowner_before\fP (const __weak_ptr< _Tp1, _Lp > &__rhs) const noexcept"
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.ti -1c
.RI "void \fBreset\fP () noexcept"
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.ti -1c
.RI "void \fBswap\fP (__weak_ptr &__s) noexcept"
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.RI "long \fBuse_count\fP () const noexcept"
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.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\&. 

.SH "Author"
.PP 
Generated automatically by Doxygen for libstdc++ from the source code\&.