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std::_Optional_base< _Tp, bool, bool >(3cxx) std::_Optional_base< _Tp, bool, bool >(3cxx)


std::_Optional_base< _Tp, bool, bool > - Class template that provides copy/move constructors of optional.


#include <optional>

Inherits std::_Optional_base_impl< _Tp, _Dp >.

Inherited by std::optional< _Inner_iter > [private], std::experimental::fundamentals_v1::optional< _Tp > [private], std::optional< _Tp > [private], and std::ranges::__detail::__non_propagating_cache< _Tp > [protected].

Public Member Functions

constexpr _Optional_base (_Optional_base &&__other) noexcept(is_nothrow_move_constructible_v< _Tp >)
constexpr _Optional_base (const _Optional_base &__other)
template<typename... _Args, enable_if_t< is_constructible_v< _Tp, _Args... >, bool > = false> constexpr _Optional_base (in_place_t, _Args &&... __args)
template<typename _Up , typename... _Args, enable_if_t< is_constructible_v< _Tp, initializer_list< _Up > &, _Args... >, bool > = false> constexpr _Optional_base (in_place_t, initializer_list< _Up > __il, _Args &&... __args)
_Optional_base & operator= (_Optional_base &&)=default
_Optional_base & operator= (const _Optional_base &)=default

Public Attributes

_Optional_payload< _Tp > _M_payload

Protected Types

using _Stored_type = remove_const_t< _Tp >

Protected Member Functions

template<typename... _Args> constexpr void _M_construct (_Args &&... __args) noexcept(is_nothrow_constructible_v< _Stored_type, _Args... >)
constexpr void _M_destruct () noexcept
constexpr const _Tp & _M_get () const noexcept
constexpr _Tp & _M_get () noexcept
constexpr bool _M_is_engaged () const noexcept
constexpr void _M_reset () noexcept

Detailed Description

template<typename _Tp, bool = is_trivially_copy_constructible_v<_Tp>, bool = is_trivially_move_constructible_v<_Tp>>

struct std::_Optional_base< _Tp, bool, bool >"Class template that provides copy/move constructors of optional.

Such a separate base class template is necessary in order to conditionally make copy/move constructors trivial.

When the contained value is trivially copy/move constructible, the copy/move constructors of _Optional_base will invoke the trivial copy/move constructor of _Optional_payload. Otherwise, they will invoke _Optional_payload(bool, const _Optional_payload&) or _Optional_payload(bool, _Optional_payload&&) to initialize the contained value, if copying/moving an engaged optional.

Whether the other special members are trivial is determined by the _Optional_payload<_Tp> specialization used for the _M_payload member.

See also

optional, _Enable_special_members


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