std::weak_ptr< _Tp > - A non-owning observer for a pointer owned by a shared_ptr.

       Generated automatically by Doxygen for libstdc++ from the source code.

                                                    libstdc++                         std::weak_ptr<_Tp>(3cxx)

template<typename_Tp>
       class std::weak_ptr< _Tp >"A non-owning observer for a pointer owned by a shared_ptr.

       Since
           C++11

       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.

       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.

       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 expired 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.

       std::weak_ptr< _Tp > - A non-owning observer for a pointer owned by a shared_ptr.

       #include <memory>

       Inherits std::__weak_ptr< _Tp, _Lp >.

   PublicTypesusingelement_type = typenameremove_extent< _Tp >::type

   PublicMemberFunctions
       template<typename_Yp , typename  = _Constructible<const shared_ptr<_Yp>&>> weak_ptr (const shared_ptr<
           _Yp > &__r) noexcept
       weak_ptr (const weak_ptr &) noexcept=default
       template<typename_Yp , typename  = _Constructible<const weak_ptr<_Yp>&>> weak_ptr (const weak_ptr< _Yp >
           &__r) noexcept
       weak_ptr (weak_ptr &&) noexcept=default
       template<typename_Yp , typename  = _Constructible<weak_ptr<_Yp>>> weak_ptr (weak_ptr< _Yp > &&__r)
           noexcept
       bool expired () const noexcept
       shared_ptr< _Tp > lock () const noexcept
       template<typename_Yp > _Assignable< const shared_ptr< _Yp > & > operator= (const shared_ptr< _Yp > &__r)
           noexcept
       weak_ptr & operator= (const weak_ptr &__r) noexcept=default
       template<typename_Yp > _Assignable< const weak_ptr< _Yp > & > operator= (const weak_ptr< _Yp > &__r)
           noexcept
       weak_ptr & operator= (weak_ptr &&__r) noexcept=default
       template<typename_Yp > _Assignable< weak_ptr< _Yp > > operator= (weak_ptr< _Yp > &&__r) noexcept
       template<typename_Tp1 > bool owner_before (const __shared_ptr< _Tp1, _Lp > &__rhs) const noexcept
       template<typename_Tp1 > bool owner_before (const __weak_ptr< _Tp1, _Lp > &__rhs) const noexcept
       voidreset () noexcept
       voidswap (__weak_ptr &__s) noexcept
       long use_count () const noexcept

   RelatedSymbols
       (Note that these are not member symbols.)
       template<typename _Tp > voidswap (weak_ptr< _Tp > &__a, weak_ptr< _Tp > &__b) noexcept
           Swap overload for weak_ptr.