9360d6cd17
The structure of these functions likely dates from the time before G++ fully supported C++14 extended constexpr, so that the throw expression had to be the operand of a conditional expression. That is not true now, so we can use a more straightforward version of the code. We can also simplify the declaration of __throw_bad_optional_access by using the C++11-style [[noreturn]] attribute so that a separate declaration isn't needed. libstdc++-v3/ChangeLog: * include/experimental/optional (__throw_bad_optional_access): Replace GNU attribute with C++11 attribute. (optional::value, optional::value_or): Use if statements instead of conditional expressions. * include/std/optional (__throw_bad_optional_access) (optional::value, optional::value_or): Likewise.
1332 lines
39 KiB
C++
1332 lines
39 KiB
C++
// <optional> -*- C++ -*-
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// Copyright (C) 2013-2021 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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/** @file include/optional
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* This is a Standard C++ Library header.
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*/
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#ifndef _GLIBCXX_OPTIONAL
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#define _GLIBCXX_OPTIONAL 1
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#pragma GCC system_header
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#if __cplusplus >= 201703L
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#include <type_traits>
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#include <exception>
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#include <new>
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#include <initializer_list>
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#include <bits/enable_special_members.h>
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#include <bits/exception_defines.h>
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#include <bits/functional_hash.h>
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#include <bits/utility.h> // in_place_t
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#if __cplusplus > 201703L
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# include <compare>
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#endif
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namespace std _GLIBCXX_VISIBILITY(default)
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{
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_GLIBCXX_BEGIN_NAMESPACE_VERSION
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/**
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* @addtogroup utilities
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* @{
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*/
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#define __cpp_lib_optional 201606L
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template<typename _Tp>
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class optional;
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/// Tag type to disengage optional objects.
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struct nullopt_t
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{
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// Do not user-declare default constructor at all for
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// optional_value = {} syntax to work.
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// nullopt_t() = delete;
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// Used for constructing nullopt.
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enum class _Construct { _Token };
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// Must be constexpr for nullopt_t to be literal.
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explicit constexpr nullopt_t(_Construct) { }
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};
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/// Tag to disengage optional objects.
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inline constexpr nullopt_t nullopt { nullopt_t::_Construct::_Token };
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/**
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* @brief Exception class thrown when a disengaged optional object is
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* dereferenced.
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* @ingroup exceptions
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*/
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class bad_optional_access : public exception
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{
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public:
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bad_optional_access() = default;
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virtual ~bad_optional_access() = default;
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const char* what() const noexcept override
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{ return "bad optional access"; }
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};
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// XXX Does not belong here.
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[[__noreturn__]] inline void
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__throw_bad_optional_access()
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{ _GLIBCXX_THROW_OR_ABORT(bad_optional_access()); }
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// This class template manages construction/destruction of
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// the contained value for a std::optional.
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template <typename _Tp>
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struct _Optional_payload_base
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{
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using _Stored_type = remove_const_t<_Tp>;
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_Optional_payload_base() = default;
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~_Optional_payload_base() = default;
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template<typename... _Args>
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constexpr
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_Optional_payload_base(in_place_t __tag, _Args&&... __args)
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: _M_payload(__tag, std::forward<_Args>(__args)...),
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_M_engaged(true)
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{ }
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template<typename _Up, typename... _Args>
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constexpr
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_Optional_payload_base(std::initializer_list<_Up> __il,
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_Args&&... __args)
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: _M_payload(__il, std::forward<_Args>(__args)...),
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_M_engaged(true)
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{ }
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// Constructor used by _Optional_base copy constructor when the
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// contained value is not trivially copy constructible.
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constexpr
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_Optional_payload_base(bool __engaged,
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const _Optional_payload_base& __other)
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{
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if (__other._M_engaged)
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this->_M_construct(__other._M_get());
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}
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// Constructor used by _Optional_base move constructor when the
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// contained value is not trivially move constructible.
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constexpr
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_Optional_payload_base(bool __engaged,
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_Optional_payload_base&& __other)
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{
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if (__other._M_engaged)
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this->_M_construct(std::move(__other._M_get()));
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}
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// Copy constructor is only used to when the contained value is
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// trivially copy constructible.
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_Optional_payload_base(const _Optional_payload_base&) = default;
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// Move constructor is only used to when the contained value is
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// trivially copy constructible.
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_Optional_payload_base(_Optional_payload_base&&) = default;
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_Optional_payload_base&
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operator=(const _Optional_payload_base&) = default;
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_Optional_payload_base&
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operator=(_Optional_payload_base&&) = default;
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// used to perform non-trivial copy assignment.
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constexpr void
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_M_copy_assign(const _Optional_payload_base& __other)
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{
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if (this->_M_engaged && __other._M_engaged)
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this->_M_get() = __other._M_get();
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else
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{
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if (__other._M_engaged)
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this->_M_construct(__other._M_get());
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else
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this->_M_reset();
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}
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}
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// used to perform non-trivial move assignment.
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constexpr void
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_M_move_assign(_Optional_payload_base&& __other)
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noexcept(__and_v<is_nothrow_move_constructible<_Tp>,
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is_nothrow_move_assignable<_Tp>>)
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{
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if (this->_M_engaged && __other._M_engaged)
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this->_M_get() = std::move(__other._M_get());
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else
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{
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if (__other._M_engaged)
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this->_M_construct(std::move(__other._M_get()));
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else
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this->_M_reset();
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}
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}
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struct _Empty_byte { };
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template<typename _Up, bool = is_trivially_destructible_v<_Up>>
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union _Storage
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{
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constexpr _Storage() noexcept : _M_empty() { }
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template<typename... _Args>
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constexpr
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_Storage(in_place_t, _Args&&... __args)
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: _M_value(std::forward<_Args>(__args)...)
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{ }
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template<typename _Vp, typename... _Args>
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constexpr
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_Storage(std::initializer_list<_Vp> __il, _Args&&... __args)
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: _M_value(__il, std::forward<_Args>(__args)...)
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{ }
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_Empty_byte _M_empty;
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_Up _M_value;
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};
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template<typename _Up>
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union _Storage<_Up, false>
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{
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constexpr _Storage() noexcept : _M_empty() { }
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template<typename... _Args>
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constexpr
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_Storage(in_place_t, _Args&&... __args)
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: _M_value(std::forward<_Args>(__args)...)
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{ }
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template<typename _Vp, typename... _Args>
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constexpr
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_Storage(std::initializer_list<_Vp> __il, _Args&&... __args)
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: _M_value(__il, std::forward<_Args>(__args)...)
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{ }
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// User-provided destructor is needed when _Up has non-trivial dtor.
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~_Storage() { }
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_Empty_byte _M_empty;
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_Up _M_value;
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};
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_Storage<_Stored_type> _M_payload;
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bool _M_engaged = false;
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template<typename... _Args>
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void
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_M_construct(_Args&&... __args)
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noexcept(is_nothrow_constructible_v<_Stored_type, _Args...>)
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{
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::new ((void *) std::__addressof(this->_M_payload))
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_Stored_type(std::forward<_Args>(__args)...);
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this->_M_engaged = true;
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}
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constexpr void
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_M_destroy() noexcept
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{
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_M_engaged = false;
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_M_payload._M_value.~_Stored_type();
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}
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// The _M_get() operations have _M_engaged as a precondition.
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// They exist to access the contained value with the appropriate
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// const-qualification, because _M_payload has had the const removed.
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constexpr _Tp&
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_M_get() noexcept
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{ return this->_M_payload._M_value; }
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constexpr const _Tp&
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_M_get() const noexcept
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{ return this->_M_payload._M_value; }
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// _M_reset is a 'safe' operation with no precondition.
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constexpr void
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_M_reset() noexcept
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{
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if (this->_M_engaged)
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_M_destroy();
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}
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};
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// Class template that manages the payload for optionals.
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template <typename _Tp,
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bool /*_HasTrivialDestructor*/ =
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is_trivially_destructible_v<_Tp>,
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bool /*_HasTrivialCopy */ =
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is_trivially_copy_assignable_v<_Tp>
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&& is_trivially_copy_constructible_v<_Tp>,
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bool /*_HasTrivialMove */ =
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is_trivially_move_assignable_v<_Tp>
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&& is_trivially_move_constructible_v<_Tp>>
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struct _Optional_payload;
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// Payload for potentially-constexpr optionals (trivial copy/move/destroy).
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template <typename _Tp>
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struct _Optional_payload<_Tp, true, true, true>
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: _Optional_payload_base<_Tp>
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{
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using _Optional_payload_base<_Tp>::_Optional_payload_base;
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_Optional_payload() = default;
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};
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// Payload for optionals with non-trivial copy construction/assignment.
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template <typename _Tp>
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struct _Optional_payload<_Tp, true, false, true>
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: _Optional_payload_base<_Tp>
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{
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using _Optional_payload_base<_Tp>::_Optional_payload_base;
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_Optional_payload() = default;
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~_Optional_payload() = default;
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_Optional_payload(const _Optional_payload&) = default;
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_Optional_payload(_Optional_payload&&) = default;
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_Optional_payload& operator=(_Optional_payload&&) = default;
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// Non-trivial copy assignment.
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constexpr
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_Optional_payload&
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operator=(const _Optional_payload& __other)
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{
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this->_M_copy_assign(__other);
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return *this;
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}
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};
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// Payload for optionals with non-trivial move construction/assignment.
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template <typename _Tp>
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struct _Optional_payload<_Tp, true, true, false>
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: _Optional_payload_base<_Tp>
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{
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using _Optional_payload_base<_Tp>::_Optional_payload_base;
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_Optional_payload() = default;
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~_Optional_payload() = default;
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_Optional_payload(const _Optional_payload&) = default;
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_Optional_payload(_Optional_payload&&) = default;
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_Optional_payload& operator=(const _Optional_payload&) = default;
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// Non-trivial move assignment.
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constexpr
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_Optional_payload&
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operator=(_Optional_payload&& __other)
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noexcept(__and_v<is_nothrow_move_constructible<_Tp>,
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is_nothrow_move_assignable<_Tp>>)
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{
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this->_M_move_assign(std::move(__other));
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return *this;
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}
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};
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// Payload for optionals with non-trivial copy and move assignment.
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template <typename _Tp>
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struct _Optional_payload<_Tp, true, false, false>
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: _Optional_payload_base<_Tp>
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{
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using _Optional_payload_base<_Tp>::_Optional_payload_base;
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_Optional_payload() = default;
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~_Optional_payload() = default;
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_Optional_payload(const _Optional_payload&) = default;
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_Optional_payload(_Optional_payload&&) = default;
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// Non-trivial copy assignment.
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constexpr
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_Optional_payload&
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operator=(const _Optional_payload& __other)
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{
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this->_M_copy_assign(__other);
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return *this;
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}
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// Non-trivial move assignment.
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constexpr
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_Optional_payload&
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operator=(_Optional_payload&& __other)
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noexcept(__and_v<is_nothrow_move_constructible<_Tp>,
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is_nothrow_move_assignable<_Tp>>)
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{
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this->_M_move_assign(std::move(__other));
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return *this;
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}
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};
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// Payload for optionals with non-trivial destructors.
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template <typename _Tp, bool _Copy, bool _Move>
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struct _Optional_payload<_Tp, false, _Copy, _Move>
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: _Optional_payload<_Tp, true, false, false>
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{
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// Base class implements all the constructors and assignment operators:
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using _Optional_payload<_Tp, true, false, false>::_Optional_payload;
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_Optional_payload() = default;
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_Optional_payload(const _Optional_payload&) = default;
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_Optional_payload(_Optional_payload&&) = default;
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_Optional_payload& operator=(const _Optional_payload&) = default;
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_Optional_payload& operator=(_Optional_payload&&) = default;
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// Destructor needs to destroy the contained value:
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~_Optional_payload() { this->_M_reset(); }
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};
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// Common base class for _Optional_base<T> to avoid repeating these
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// member functions in each specialization.
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template<typename _Tp, typename _Dp>
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class _Optional_base_impl
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{
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protected:
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using _Stored_type = remove_const_t<_Tp>;
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// The _M_construct operation has !_M_engaged as a precondition
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// while _M_destruct has _M_engaged as a precondition.
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template<typename... _Args>
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void
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_M_construct(_Args&&... __args)
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noexcept(is_nothrow_constructible_v<_Stored_type, _Args...>)
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{
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::new
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(std::__addressof(static_cast<_Dp*>(this)->_M_payload._M_payload))
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_Stored_type(std::forward<_Args>(__args)...);
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static_cast<_Dp*>(this)->_M_payload._M_engaged = true;
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}
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void
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_M_destruct() noexcept
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{ static_cast<_Dp*>(this)->_M_payload._M_destroy(); }
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// _M_reset is a 'safe' operation with no precondition.
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constexpr void
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_M_reset() noexcept
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{ static_cast<_Dp*>(this)->_M_payload._M_reset(); }
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constexpr bool _M_is_engaged() const noexcept
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{ return static_cast<const _Dp*>(this)->_M_payload._M_engaged; }
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// The _M_get operations have _M_engaged as a precondition.
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constexpr _Tp&
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_M_get() noexcept
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{
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__glibcxx_assert(this->_M_is_engaged());
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return static_cast<_Dp*>(this)->_M_payload._M_get();
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}
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constexpr const _Tp&
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_M_get() const noexcept
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{
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__glibcxx_assert(this->_M_is_engaged());
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return static_cast<const _Dp*>(this)->_M_payload._M_get();
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}
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};
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/**
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* @brief Class template that provides copy/move constructors of optional.
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*
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* Such a separate base class template is necessary in order to
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* conditionally make copy/move constructors trivial.
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*
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* When the contained value is trivially copy/move constructible,
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* the copy/move constructors of _Optional_base will invoke the
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* trivial copy/move constructor of _Optional_payload. Otherwise,
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* they will invoke _Optional_payload(bool, const _Optional_payload&)
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* or _Optional_payload(bool, _Optional_payload&&) to initialize
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* the contained value, if copying/moving an engaged optional.
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*
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* Whether the other special members are trivial is determined by the
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* _Optional_payload<_Tp> specialization used for the _M_payload member.
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*
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* @see optional, _Enable_special_members
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*/
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template<typename _Tp,
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bool = is_trivially_copy_constructible_v<_Tp>,
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bool = is_trivially_move_constructible_v<_Tp>>
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struct _Optional_base
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: _Optional_base_impl<_Tp, _Optional_base<_Tp>>
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{
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// Constructors for disengaged optionals.
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constexpr _Optional_base() = default;
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// Constructors for engaged optionals.
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template<typename... _Args,
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enable_if_t<is_constructible_v<_Tp, _Args...>, bool> = false>
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constexpr explicit
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_Optional_base(in_place_t, _Args&&... __args)
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: _M_payload(in_place, std::forward<_Args>(__args)...)
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{ }
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template<typename _Up, typename... _Args,
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enable_if_t<is_constructible_v<_Tp,
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initializer_list<_Up>&,
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_Args...>, bool> = false>
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constexpr explicit
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_Optional_base(in_place_t,
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initializer_list<_Up> __il,
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_Args&&... __args)
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: _M_payload(in_place, __il, std::forward<_Args>(__args)...)
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{ }
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// Copy and move constructors.
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constexpr
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_Optional_base(const _Optional_base& __other)
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: _M_payload(__other._M_payload._M_engaged, __other._M_payload)
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{ }
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constexpr
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_Optional_base(_Optional_base&& __other)
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noexcept(is_nothrow_move_constructible_v<_Tp>)
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: _M_payload(__other._M_payload._M_engaged,
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std::move(__other._M_payload))
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{ }
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// Assignment operators.
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_Optional_base& operator=(const _Optional_base&) = default;
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_Optional_base& operator=(_Optional_base&&) = default;
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_Optional_payload<_Tp> _M_payload;
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};
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template<typename _Tp>
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|
struct _Optional_base<_Tp, false, true>
|
|
: _Optional_base_impl<_Tp, _Optional_base<_Tp>>
|
|
{
|
|
// Constructors for disengaged optionals.
|
|
constexpr _Optional_base() = default;
|
|
|
|
// Constructors for engaged optionals.
|
|
template<typename... _Args,
|
|
enable_if_t<is_constructible_v<_Tp, _Args...>, bool> = false>
|
|
constexpr explicit
|
|
_Optional_base(in_place_t, _Args&&... __args)
|
|
: _M_payload(in_place, std::forward<_Args>(__args)...)
|
|
{ }
|
|
|
|
template<typename _Up, typename... _Args,
|
|
enable_if_t<is_constructible_v<_Tp,
|
|
initializer_list<_Up>&,
|
|
_Args...>, bool> = false>
|
|
constexpr explicit
|
|
_Optional_base(in_place_t,
|
|
initializer_list<_Up> __il,
|
|
_Args... __args)
|
|
: _M_payload(in_place, __il, std::forward<_Args>(__args)...)
|
|
{ }
|
|
|
|
// Copy and move constructors.
|
|
constexpr _Optional_base(const _Optional_base& __other)
|
|
: _M_payload(__other._M_payload._M_engaged, __other._M_payload)
|
|
{ }
|
|
|
|
constexpr _Optional_base(_Optional_base&& __other) = default;
|
|
|
|
// Assignment operators.
|
|
_Optional_base& operator=(const _Optional_base&) = default;
|
|
_Optional_base& operator=(_Optional_base&&) = default;
|
|
|
|
_Optional_payload<_Tp> _M_payload;
|
|
};
|
|
|
|
template<typename _Tp>
|
|
struct _Optional_base<_Tp, true, false>
|
|
: _Optional_base_impl<_Tp, _Optional_base<_Tp>>
|
|
{
|
|
// Constructors for disengaged optionals.
|
|
constexpr _Optional_base() = default;
|
|
|
|
// Constructors for engaged optionals.
|
|
template<typename... _Args,
|
|
enable_if_t<is_constructible_v<_Tp, _Args...>, bool> = false>
|
|
constexpr explicit
|
|
_Optional_base(in_place_t, _Args&&... __args)
|
|
: _M_payload(in_place, std::forward<_Args>(__args)...)
|
|
{ }
|
|
|
|
template<typename _Up, typename... _Args,
|
|
enable_if_t<is_constructible_v<_Tp,
|
|
initializer_list<_Up>&,
|
|
_Args...>, bool> = false>
|
|
constexpr explicit
|
|
_Optional_base(in_place_t,
|
|
initializer_list<_Up> __il,
|
|
_Args&&... __args)
|
|
: _M_payload(in_place, __il, std::forward<_Args>(__args)...)
|
|
{ }
|
|
|
|
// Copy and move constructors.
|
|
constexpr _Optional_base(const _Optional_base& __other) = default;
|
|
|
|
constexpr
|
|
_Optional_base(_Optional_base&& __other)
|
|
noexcept(is_nothrow_move_constructible_v<_Tp>)
|
|
: _M_payload(__other._M_payload._M_engaged,
|
|
std::move(__other._M_payload))
|
|
{ }
|
|
|
|
// Assignment operators.
|
|
_Optional_base& operator=(const _Optional_base&) = default;
|
|
_Optional_base& operator=(_Optional_base&&) = default;
|
|
|
|
_Optional_payload<_Tp> _M_payload;
|
|
};
|
|
|
|
template<typename _Tp>
|
|
struct _Optional_base<_Tp, true, true>
|
|
: _Optional_base_impl<_Tp, _Optional_base<_Tp>>
|
|
{
|
|
// Constructors for disengaged optionals.
|
|
constexpr _Optional_base() = default;
|
|
|
|
// Constructors for engaged optionals.
|
|
template<typename... _Args,
|
|
enable_if_t<is_constructible_v<_Tp, _Args...>, bool> = false>
|
|
constexpr explicit
|
|
_Optional_base(in_place_t, _Args&&... __args)
|
|
: _M_payload(in_place, std::forward<_Args>(__args)...)
|
|
{ }
|
|
|
|
template<typename _Up, typename... _Args,
|
|
enable_if_t<is_constructible_v<_Tp,
|
|
initializer_list<_Up>&,
|
|
_Args...>, bool> = false>
|
|
constexpr explicit
|
|
_Optional_base(in_place_t,
|
|
initializer_list<_Up> __il,
|
|
_Args&&... __args)
|
|
: _M_payload(in_place, __il, std::forward<_Args>(__args)...)
|
|
{ }
|
|
|
|
// Copy and move constructors.
|
|
constexpr _Optional_base(const _Optional_base& __other) = default;
|
|
constexpr _Optional_base(_Optional_base&& __other) = default;
|
|
|
|
// Assignment operators.
|
|
_Optional_base& operator=(const _Optional_base&) = default;
|
|
_Optional_base& operator=(_Optional_base&&) = default;
|
|
|
|
_Optional_payload<_Tp> _M_payload;
|
|
};
|
|
|
|
template<typename _Tp>
|
|
class optional;
|
|
|
|
template<typename _Tp, typename _Up>
|
|
using __converts_from_optional =
|
|
__or_<is_constructible<_Tp, const optional<_Up>&>,
|
|
is_constructible<_Tp, optional<_Up>&>,
|
|
is_constructible<_Tp, const optional<_Up>&&>,
|
|
is_constructible<_Tp, optional<_Up>&&>,
|
|
is_convertible<const optional<_Up>&, _Tp>,
|
|
is_convertible<optional<_Up>&, _Tp>,
|
|
is_convertible<const optional<_Up>&&, _Tp>,
|
|
is_convertible<optional<_Up>&&, _Tp>>;
|
|
|
|
template<typename _Tp, typename _Up>
|
|
using __assigns_from_optional =
|
|
__or_<is_assignable<_Tp&, const optional<_Up>&>,
|
|
is_assignable<_Tp&, optional<_Up>&>,
|
|
is_assignable<_Tp&, const optional<_Up>&&>,
|
|
is_assignable<_Tp&, optional<_Up>&&>>;
|
|
|
|
/**
|
|
* @brief Class template for optional values.
|
|
*/
|
|
template<typename _Tp>
|
|
class optional
|
|
: private _Optional_base<_Tp>,
|
|
private _Enable_copy_move<
|
|
// Copy constructor.
|
|
is_copy_constructible_v<_Tp>,
|
|
// Copy assignment.
|
|
__and_v<is_copy_constructible<_Tp>, is_copy_assignable<_Tp>>,
|
|
// Move constructor.
|
|
is_move_constructible_v<_Tp>,
|
|
// Move assignment.
|
|
__and_v<is_move_constructible<_Tp>, is_move_assignable<_Tp>>,
|
|
// Unique tag type.
|
|
optional<_Tp>>
|
|
{
|
|
static_assert(!is_same_v<remove_cv_t<_Tp>, nullopt_t>);
|
|
static_assert(!is_same_v<remove_cv_t<_Tp>, in_place_t>);
|
|
static_assert(!is_reference_v<_Tp>);
|
|
|
|
private:
|
|
using _Base = _Optional_base<_Tp>;
|
|
|
|
// SFINAE helpers
|
|
template<typename _Up>
|
|
using __not_self = __not_<is_same<optional, __remove_cvref_t<_Up>>>;
|
|
template<typename _Up>
|
|
using __not_tag = __not_<is_same<in_place_t, __remove_cvref_t<_Up>>>;
|
|
template<typename... _Cond>
|
|
using _Requires = enable_if_t<__and_v<_Cond...>, bool>;
|
|
|
|
public:
|
|
using value_type = _Tp;
|
|
|
|
constexpr optional() noexcept { }
|
|
|
|
constexpr optional(nullopt_t) noexcept { }
|
|
|
|
// Converting constructors for engaged optionals.
|
|
template<typename _Up = _Tp,
|
|
_Requires<__not_self<_Up>, __not_tag<_Up>,
|
|
is_constructible<_Tp, _Up>,
|
|
is_convertible<_Up, _Tp>> = true>
|
|
constexpr
|
|
optional(_Up&& __t)
|
|
noexcept(is_nothrow_constructible_v<_Tp, _Up>)
|
|
: _Base(std::in_place, std::forward<_Up>(__t)) { }
|
|
|
|
template<typename _Up = _Tp,
|
|
_Requires<__not_self<_Up>, __not_tag<_Up>,
|
|
is_constructible<_Tp, _Up>,
|
|
__not_<is_convertible<_Up, _Tp>>> = false>
|
|
explicit constexpr
|
|
optional(_Up&& __t)
|
|
noexcept(is_nothrow_constructible_v<_Tp, _Up>)
|
|
: _Base(std::in_place, std::forward<_Up>(__t)) { }
|
|
|
|
template<typename _Up,
|
|
_Requires<__not_<is_same<_Tp, _Up>>,
|
|
is_constructible<_Tp, const _Up&>,
|
|
is_convertible<const _Up&, _Tp>,
|
|
__not_<__converts_from_optional<_Tp, _Up>>> = true>
|
|
constexpr
|
|
optional(const optional<_Up>& __t)
|
|
noexcept(is_nothrow_constructible_v<_Tp, const _Up&>)
|
|
{
|
|
if (__t)
|
|
emplace(*__t);
|
|
}
|
|
|
|
template<typename _Up,
|
|
_Requires<__not_<is_same<_Tp, _Up>>,
|
|
is_constructible<_Tp, const _Up&>,
|
|
__not_<is_convertible<const _Up&, _Tp>>,
|
|
__not_<__converts_from_optional<_Tp, _Up>>> = false>
|
|
explicit constexpr
|
|
optional(const optional<_Up>& __t)
|
|
noexcept(is_nothrow_constructible_v<_Tp, const _Up&>)
|
|
{
|
|
if (__t)
|
|
emplace(*__t);
|
|
}
|
|
|
|
template<typename _Up,
|
|
_Requires<__not_<is_same<_Tp, _Up>>,
|
|
is_constructible<_Tp, _Up>,
|
|
is_convertible<_Up, _Tp>,
|
|
__not_<__converts_from_optional<_Tp, _Up>>> = true>
|
|
constexpr
|
|
optional(optional<_Up>&& __t)
|
|
noexcept(is_nothrow_constructible_v<_Tp, _Up>)
|
|
{
|
|
if (__t)
|
|
emplace(std::move(*__t));
|
|
}
|
|
|
|
template<typename _Up,
|
|
_Requires<__not_<is_same<_Tp, _Up>>,
|
|
is_constructible<_Tp, _Up>,
|
|
__not_<is_convertible<_Up, _Tp>>,
|
|
__not_<__converts_from_optional<_Tp, _Up>>> = false>
|
|
explicit constexpr
|
|
optional(optional<_Up>&& __t)
|
|
noexcept(is_nothrow_constructible_v<_Tp, _Up>)
|
|
{
|
|
if (__t)
|
|
emplace(std::move(*__t));
|
|
}
|
|
|
|
template<typename... _Args,
|
|
_Requires<is_constructible<_Tp, _Args...>> = false>
|
|
explicit constexpr
|
|
optional(in_place_t, _Args&&... __args)
|
|
noexcept(is_nothrow_constructible_v<_Tp, _Args...>)
|
|
: _Base(std::in_place, std::forward<_Args>(__args)...) { }
|
|
|
|
template<typename _Up, typename... _Args,
|
|
_Requires<is_constructible<_Tp,
|
|
initializer_list<_Up>&,
|
|
_Args...>> = false>
|
|
explicit constexpr
|
|
optional(in_place_t, initializer_list<_Up> __il, _Args&&... __args)
|
|
noexcept(is_nothrow_constructible_v<_Tp, initializer_list<_Up>&,
|
|
_Args...>)
|
|
: _Base(std::in_place, __il, std::forward<_Args>(__args)...) { }
|
|
|
|
|
|
// Assignment operators.
|
|
optional&
|
|
operator=(nullopt_t) noexcept
|
|
{
|
|
this->_M_reset();
|
|
return *this;
|
|
}
|
|
|
|
template<typename _Up = _Tp>
|
|
enable_if_t<__and_v<__not_self<_Up>,
|
|
__not_<__and_<is_scalar<_Tp>,
|
|
is_same<_Tp, decay_t<_Up>>>>,
|
|
is_constructible<_Tp, _Up>,
|
|
is_assignable<_Tp&, _Up>>,
|
|
optional&>
|
|
operator=(_Up&& __u)
|
|
noexcept(__and_v<is_nothrow_constructible<_Tp, _Up>,
|
|
is_nothrow_assignable<_Tp&, _Up>>)
|
|
{
|
|
if (this->_M_is_engaged())
|
|
this->_M_get() = std::forward<_Up>(__u);
|
|
else
|
|
this->_M_construct(std::forward<_Up>(__u));
|
|
|
|
return *this;
|
|
}
|
|
|
|
template<typename _Up>
|
|
enable_if_t<__and_v<__not_<is_same<_Tp, _Up>>,
|
|
is_constructible<_Tp, const _Up&>,
|
|
is_assignable<_Tp&, const _Up&>,
|
|
__not_<__converts_from_optional<_Tp, _Up>>,
|
|
__not_<__assigns_from_optional<_Tp, _Up>>>,
|
|
optional&>
|
|
operator=(const optional<_Up>& __u)
|
|
noexcept(__and_v<is_nothrow_constructible<_Tp, const _Up&>,
|
|
is_nothrow_assignable<_Tp&, const _Up&>>)
|
|
{
|
|
if (__u)
|
|
{
|
|
if (this->_M_is_engaged())
|
|
this->_M_get() = *__u;
|
|
else
|
|
this->_M_construct(*__u);
|
|
}
|
|
else
|
|
{
|
|
this->_M_reset();
|
|
}
|
|
return *this;
|
|
}
|
|
|
|
template<typename _Up>
|
|
enable_if_t<__and_v<__not_<is_same<_Tp, _Up>>,
|
|
is_constructible<_Tp, _Up>,
|
|
is_assignable<_Tp&, _Up>,
|
|
__not_<__converts_from_optional<_Tp, _Up>>,
|
|
__not_<__assigns_from_optional<_Tp, _Up>>>,
|
|
optional&>
|
|
operator=(optional<_Up>&& __u)
|
|
noexcept(__and_v<is_nothrow_constructible<_Tp, _Up>,
|
|
is_nothrow_assignable<_Tp&, _Up>>)
|
|
{
|
|
if (__u)
|
|
{
|
|
if (this->_M_is_engaged())
|
|
this->_M_get() = std::move(*__u);
|
|
else
|
|
this->_M_construct(std::move(*__u));
|
|
}
|
|
else
|
|
{
|
|
this->_M_reset();
|
|
}
|
|
|
|
return *this;
|
|
}
|
|
|
|
template<typename... _Args>
|
|
enable_if_t<is_constructible_v<_Tp, _Args...>, _Tp&>
|
|
emplace(_Args&&... __args)
|
|
noexcept(is_nothrow_constructible_v<_Tp, _Args...>)
|
|
{
|
|
this->_M_reset();
|
|
this->_M_construct(std::forward<_Args>(__args)...);
|
|
return this->_M_get();
|
|
}
|
|
|
|
template<typename _Up, typename... _Args>
|
|
enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
|
|
_Tp&>
|
|
emplace(initializer_list<_Up> __il, _Args&&... __args)
|
|
noexcept(is_nothrow_constructible_v<_Tp, initializer_list<_Up>&,
|
|
_Args...>)
|
|
{
|
|
this->_M_reset();
|
|
this->_M_construct(__il, std::forward<_Args>(__args)...);
|
|
return this->_M_get();
|
|
}
|
|
|
|
// Destructor is implicit, implemented in _Optional_base.
|
|
|
|
// Swap.
|
|
void
|
|
swap(optional& __other)
|
|
noexcept(is_nothrow_move_constructible_v<_Tp>
|
|
&& is_nothrow_swappable_v<_Tp>)
|
|
{
|
|
using std::swap;
|
|
|
|
if (this->_M_is_engaged() && __other._M_is_engaged())
|
|
swap(this->_M_get(), __other._M_get());
|
|
else if (this->_M_is_engaged())
|
|
{
|
|
__other._M_construct(std::move(this->_M_get()));
|
|
this->_M_destruct();
|
|
}
|
|
else if (__other._M_is_engaged())
|
|
{
|
|
this->_M_construct(std::move(__other._M_get()));
|
|
__other._M_destruct();
|
|
}
|
|
}
|
|
|
|
// Observers.
|
|
constexpr const _Tp*
|
|
operator->() const noexcept
|
|
{ return std::__addressof(this->_M_get()); }
|
|
|
|
constexpr _Tp*
|
|
operator->() noexcept
|
|
{ return std::__addressof(this->_M_get()); }
|
|
|
|
constexpr const _Tp&
|
|
operator*() const& noexcept
|
|
{ return this->_M_get(); }
|
|
|
|
constexpr _Tp&
|
|
operator*()& noexcept
|
|
{ return this->_M_get(); }
|
|
|
|
constexpr _Tp&&
|
|
operator*()&& noexcept
|
|
{ return std::move(this->_M_get()); }
|
|
|
|
constexpr const _Tp&&
|
|
operator*() const&& noexcept
|
|
{ return std::move(this->_M_get()); }
|
|
|
|
constexpr explicit operator bool() const noexcept
|
|
{ return this->_M_is_engaged(); }
|
|
|
|
constexpr bool has_value() const noexcept
|
|
{ return this->_M_is_engaged(); }
|
|
|
|
constexpr const _Tp&
|
|
value() const&
|
|
{
|
|
if (this->_M_is_engaged())
|
|
return this->_M_get();
|
|
__throw_bad_optional_access();
|
|
}
|
|
|
|
constexpr _Tp&
|
|
value()&
|
|
{
|
|
if (this->_M_is_engaged())
|
|
return this->_M_get();
|
|
__throw_bad_optional_access();
|
|
}
|
|
|
|
constexpr _Tp&&
|
|
value()&&
|
|
{
|
|
if (this->_M_is_engaged())
|
|
return std::move(this->_M_get());
|
|
__throw_bad_optional_access();
|
|
}
|
|
|
|
constexpr const _Tp&&
|
|
value() const&&
|
|
{
|
|
if (this->_M_is_engaged())
|
|
return std::move(this->_M_get());
|
|
__throw_bad_optional_access();
|
|
}
|
|
|
|
template<typename _Up>
|
|
constexpr _Tp
|
|
value_or(_Up&& __u) const&
|
|
{
|
|
static_assert(is_copy_constructible_v<_Tp>);
|
|
static_assert(is_convertible_v<_Up&&, _Tp>);
|
|
|
|
if (this->_M_is_engaged())
|
|
return this->_M_get();
|
|
else
|
|
return static_cast<_Tp>(std::forward<_Up>(__u));
|
|
}
|
|
|
|
template<typename _Up>
|
|
constexpr _Tp
|
|
value_or(_Up&& __u) &&
|
|
{
|
|
static_assert(is_move_constructible_v<_Tp>);
|
|
static_assert(is_convertible_v<_Up&&, _Tp>);
|
|
|
|
if (this->_M_is_engaged())
|
|
return std::move(this->_M_get());
|
|
else
|
|
return static_cast<_Tp>(std::forward<_Up>(__u));
|
|
}
|
|
|
|
void reset() noexcept { this->_M_reset(); }
|
|
};
|
|
|
|
template<typename _Tp>
|
|
using __optional_relop_t =
|
|
enable_if_t<is_convertible<_Tp, bool>::value, bool>;
|
|
|
|
template<typename _Tp, typename _Up>
|
|
using __optional_eq_t = __optional_relop_t<
|
|
decltype(std::declval<const _Tp&>() == std::declval<const _Up&>())
|
|
>;
|
|
|
|
template<typename _Tp, typename _Up>
|
|
using __optional_ne_t = __optional_relop_t<
|
|
decltype(std::declval<const _Tp&>() != std::declval<const _Up&>())
|
|
>;
|
|
|
|
template<typename _Tp, typename _Up>
|
|
using __optional_lt_t = __optional_relop_t<
|
|
decltype(std::declval<const _Tp&>() < std::declval<const _Up&>())
|
|
>;
|
|
|
|
template<typename _Tp, typename _Up>
|
|
using __optional_gt_t = __optional_relop_t<
|
|
decltype(std::declval<const _Tp&>() > std::declval<const _Up&>())
|
|
>;
|
|
|
|
template<typename _Tp, typename _Up>
|
|
using __optional_le_t = __optional_relop_t<
|
|
decltype(std::declval<const _Tp&>() <= std::declval<const _Up&>())
|
|
>;
|
|
|
|
template<typename _Tp, typename _Up>
|
|
using __optional_ge_t = __optional_relop_t<
|
|
decltype(std::declval<const _Tp&>() >= std::declval<const _Up&>())
|
|
>;
|
|
|
|
// Comparisons between optional values.
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator==(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
|
|
-> __optional_eq_t<_Tp, _Up>
|
|
{
|
|
return static_cast<bool>(__lhs) == static_cast<bool>(__rhs)
|
|
&& (!__lhs || *__lhs == *__rhs);
|
|
}
|
|
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator!=(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
|
|
-> __optional_ne_t<_Tp, _Up>
|
|
{
|
|
return static_cast<bool>(__lhs) != static_cast<bool>(__rhs)
|
|
|| (static_cast<bool>(__lhs) && *__lhs != *__rhs);
|
|
}
|
|
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator<(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
|
|
-> __optional_lt_t<_Tp, _Up>
|
|
{
|
|
return static_cast<bool>(__rhs) && (!__lhs || *__lhs < *__rhs);
|
|
}
|
|
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator>(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
|
|
-> __optional_gt_t<_Tp, _Up>
|
|
{
|
|
return static_cast<bool>(__lhs) && (!__rhs || *__lhs > *__rhs);
|
|
}
|
|
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator<=(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
|
|
-> __optional_le_t<_Tp, _Up>
|
|
{
|
|
return !__lhs || (static_cast<bool>(__rhs) && *__lhs <= *__rhs);
|
|
}
|
|
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator>=(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
|
|
-> __optional_ge_t<_Tp, _Up>
|
|
{
|
|
return !__rhs || (static_cast<bool>(__lhs) && *__lhs >= *__rhs);
|
|
}
|
|
|
|
#ifdef __cpp_lib_three_way_comparison
|
|
template<typename _Tp, three_way_comparable_with<_Tp> _Up>
|
|
constexpr compare_three_way_result_t<_Tp, _Up>
|
|
operator<=>(const optional<_Tp>& __x, const optional<_Up>& __y)
|
|
{
|
|
return __x && __y ? *__x <=> *__y : bool(__x) <=> bool(__y);
|
|
}
|
|
#endif
|
|
|
|
// Comparisons with nullopt.
|
|
template<typename _Tp>
|
|
constexpr bool
|
|
operator==(const optional<_Tp>& __lhs, nullopt_t) noexcept
|
|
{ return !__lhs; }
|
|
|
|
#ifdef __cpp_lib_three_way_comparison
|
|
template<typename _Tp>
|
|
constexpr strong_ordering
|
|
operator<=>(const optional<_Tp>& __x, nullopt_t) noexcept
|
|
{ return bool(__x) <=> false; }
|
|
#else
|
|
template<typename _Tp>
|
|
constexpr bool
|
|
operator==(nullopt_t, const optional<_Tp>& __rhs) noexcept
|
|
{ return !__rhs; }
|
|
|
|
template<typename _Tp>
|
|
constexpr bool
|
|
operator!=(const optional<_Tp>& __lhs, nullopt_t) noexcept
|
|
{ return static_cast<bool>(__lhs); }
|
|
|
|
template<typename _Tp>
|
|
constexpr bool
|
|
operator!=(nullopt_t, const optional<_Tp>& __rhs) noexcept
|
|
{ return static_cast<bool>(__rhs); }
|
|
|
|
template<typename _Tp>
|
|
constexpr bool
|
|
operator<(const optional<_Tp>& /* __lhs */, nullopt_t) noexcept
|
|
{ return false; }
|
|
|
|
template<typename _Tp>
|
|
constexpr bool
|
|
operator<(nullopt_t, const optional<_Tp>& __rhs) noexcept
|
|
{ return static_cast<bool>(__rhs); }
|
|
|
|
template<typename _Tp>
|
|
constexpr bool
|
|
operator>(const optional<_Tp>& __lhs, nullopt_t) noexcept
|
|
{ return static_cast<bool>(__lhs); }
|
|
|
|
template<typename _Tp>
|
|
constexpr bool
|
|
operator>(nullopt_t, const optional<_Tp>& /* __rhs */) noexcept
|
|
{ return false; }
|
|
|
|
template<typename _Tp>
|
|
constexpr bool
|
|
operator<=(const optional<_Tp>& __lhs, nullopt_t) noexcept
|
|
{ return !__lhs; }
|
|
|
|
template<typename _Tp>
|
|
constexpr bool
|
|
operator<=(nullopt_t, const optional<_Tp>& /* __rhs */) noexcept
|
|
{ return true; }
|
|
|
|
template<typename _Tp>
|
|
constexpr bool
|
|
operator>=(const optional<_Tp>& /* __lhs */, nullopt_t) noexcept
|
|
{ return true; }
|
|
|
|
template<typename _Tp>
|
|
constexpr bool
|
|
operator>=(nullopt_t, const optional<_Tp>& __rhs) noexcept
|
|
{ return !__rhs; }
|
|
#endif // three-way-comparison
|
|
|
|
// Comparisons with value type.
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator==(const optional<_Tp>& __lhs, const _Up& __rhs)
|
|
-> __optional_eq_t<_Tp, _Up>
|
|
{ return __lhs && *__lhs == __rhs; }
|
|
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator==(const _Up& __lhs, const optional<_Tp>& __rhs)
|
|
-> __optional_eq_t<_Up, _Tp>
|
|
{ return __rhs && __lhs == *__rhs; }
|
|
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator!=(const optional<_Tp>& __lhs, const _Up& __rhs)
|
|
-> __optional_ne_t<_Tp, _Up>
|
|
{ return !__lhs || *__lhs != __rhs; }
|
|
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator!=(const _Up& __lhs, const optional<_Tp>& __rhs)
|
|
-> __optional_ne_t<_Up, _Tp>
|
|
{ return !__rhs || __lhs != *__rhs; }
|
|
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator<(const optional<_Tp>& __lhs, const _Up& __rhs)
|
|
-> __optional_lt_t<_Tp, _Up>
|
|
{ return !__lhs || *__lhs < __rhs; }
|
|
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator<(const _Up& __lhs, const optional<_Tp>& __rhs)
|
|
-> __optional_lt_t<_Up, _Tp>
|
|
{ return __rhs && __lhs < *__rhs; }
|
|
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator>(const optional<_Tp>& __lhs, const _Up& __rhs)
|
|
-> __optional_gt_t<_Tp, _Up>
|
|
{ return __lhs && *__lhs > __rhs; }
|
|
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator>(const _Up& __lhs, const optional<_Tp>& __rhs)
|
|
-> __optional_gt_t<_Up, _Tp>
|
|
{ return !__rhs || __lhs > *__rhs; }
|
|
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator<=(const optional<_Tp>& __lhs, const _Up& __rhs)
|
|
-> __optional_le_t<_Tp, _Up>
|
|
{ return !__lhs || *__lhs <= __rhs; }
|
|
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator<=(const _Up& __lhs, const optional<_Tp>& __rhs)
|
|
-> __optional_le_t<_Up, _Tp>
|
|
{ return __rhs && __lhs <= *__rhs; }
|
|
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator>=(const optional<_Tp>& __lhs, const _Up& __rhs)
|
|
-> __optional_ge_t<_Tp, _Up>
|
|
{ return __lhs && *__lhs >= __rhs; }
|
|
|
|
template<typename _Tp, typename _Up>
|
|
constexpr auto
|
|
operator>=(const _Up& __lhs, const optional<_Tp>& __rhs)
|
|
-> __optional_ge_t<_Up, _Tp>
|
|
{ return !__rhs || __lhs >= *__rhs; }
|
|
|
|
#ifdef __cpp_lib_three_way_comparison
|
|
template<typename _Tp>
|
|
inline constexpr bool __is_optional_v = false;
|
|
template<typename _Tp>
|
|
inline constexpr bool __is_optional_v<optional<_Tp>> = true;
|
|
|
|
template<typename _Tp, typename _Up>
|
|
requires (!__is_optional_v<_Up>)
|
|
&& three_way_comparable_with<_Tp, _Up>
|
|
constexpr compare_three_way_result_t<_Tp, _Up>
|
|
operator<=>(const optional<_Tp>& __x, const _Up& __v)
|
|
{ return bool(__x) ? *__x <=> __v : strong_ordering::less; }
|
|
#endif
|
|
|
|
// Swap and creation functions.
|
|
|
|
// _GLIBCXX_RESOLVE_LIB_DEFECTS
|
|
// 2748. swappable traits for optionals
|
|
template<typename _Tp>
|
|
inline enable_if_t<is_move_constructible_v<_Tp> && is_swappable_v<_Tp>>
|
|
swap(optional<_Tp>& __lhs, optional<_Tp>& __rhs)
|
|
noexcept(noexcept(__lhs.swap(__rhs)))
|
|
{ __lhs.swap(__rhs); }
|
|
|
|
template<typename _Tp>
|
|
enable_if_t<!(is_move_constructible_v<_Tp> && is_swappable_v<_Tp>)>
|
|
swap(optional<_Tp>&, optional<_Tp>&) = delete;
|
|
|
|
template<typename _Tp>
|
|
constexpr
|
|
enable_if_t<is_constructible_v<decay_t<_Tp>, _Tp>,
|
|
optional<decay_t<_Tp>>>
|
|
make_optional(_Tp&& __t)
|
|
noexcept(is_nothrow_constructible_v<optional<decay_t<_Tp>>, _Tp>)
|
|
{ return optional<decay_t<_Tp>>{ std::forward<_Tp>(__t) }; }
|
|
|
|
template<typename _Tp, typename... _Args>
|
|
constexpr
|
|
enable_if_t<is_constructible_v<_Tp, _Args...>,
|
|
optional<_Tp>>
|
|
make_optional(_Args&&... __args)
|
|
noexcept(is_nothrow_constructible_v<_Tp, _Args...>)
|
|
{ return optional<_Tp>{ in_place, std::forward<_Args>(__args)... }; }
|
|
|
|
template<typename _Tp, typename _Up, typename... _Args>
|
|
constexpr
|
|
enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
|
|
optional<_Tp>>
|
|
make_optional(initializer_list<_Up> __il, _Args&&... __args)
|
|
noexcept(is_nothrow_constructible_v<_Tp, initializer_list<_Up>&, _Args...>)
|
|
{ return optional<_Tp>{ in_place, __il, std::forward<_Args>(__args)... }; }
|
|
|
|
// Hash.
|
|
|
|
template<typename _Tp, typename _Up = remove_const_t<_Tp>,
|
|
bool = __poison_hash<_Up>::__enable_hash_call>
|
|
struct __optional_hash_call_base
|
|
{
|
|
size_t
|
|
operator()(const optional<_Tp>& __t) const
|
|
noexcept(noexcept(hash<_Up>{}(*__t)))
|
|
{
|
|
// We pick an arbitrary hash for disengaged optionals which hopefully
|
|
// usual values of _Tp won't typically hash to.
|
|
constexpr size_t __magic_disengaged_hash = static_cast<size_t>(-3333);
|
|
return __t ? hash<_Up>{}(*__t) : __magic_disengaged_hash;
|
|
}
|
|
};
|
|
|
|
template<typename _Tp, typename _Up>
|
|
struct __optional_hash_call_base<_Tp, _Up, false> {};
|
|
|
|
template<typename _Tp>
|
|
struct hash<optional<_Tp>>
|
|
: private __poison_hash<remove_const_t<_Tp>>,
|
|
public __optional_hash_call_base<_Tp>
|
|
{
|
|
using result_type [[__deprecated__]] = size_t;
|
|
using argument_type [[__deprecated__]] = optional<_Tp>;
|
|
};
|
|
|
|
template<typename _Tp>
|
|
struct __is_fast_hash<hash<optional<_Tp>>> : __is_fast_hash<hash<_Tp>>
|
|
{ };
|
|
|
|
/// @}
|
|
|
|
#if __cpp_deduction_guides >= 201606
|
|
template <typename _Tp> optional(_Tp) -> optional<_Tp>;
|
|
#endif
|
|
|
|
_GLIBCXX_END_NAMESPACE_VERSION
|
|
} // namespace std
|
|
|
|
#endif // C++17
|
|
|
|
#endif // _GLIBCXX_OPTIONAL
|