variant
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// <variant> -*- C++ -*-
// Copyright (C) 2016-2021 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
/** @file variant
* This is the `<variant>` C++ Library header.
*/
#ifndef _GLIBCXX_VARIANT
#define _GLIBCXX_VARIANT 1
#pragma GCC system_header
#if __cplusplus >= 201703L
#include <type_traits>
#include <utility>
#include <bits/enable_special_members.h>
#include <bits/functexcept.h>
#include <bits/move.h>
#include <bits/functional_hash.h>
#include <bits/invoke.h>
#include <ext/aligned_buffer.h>
#include <bits/parse_numbers.h>
#include <bits/stl_iterator_base_types.h>
#include <bits/stl_iterator_base_funcs.h>
#include <bits/stl_construct.h>
#if __cplusplus > 201703L
# include <compare>
#endif
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
namespace __detail
{
namespace __variant
{
template<size_t _Np, typename... _Types>
struct _Nth_type;
template<size_t _Np, typename _First, typename... _Rest>
struct _Nth_type<_Np, _First, _Rest...>
: _Nth_type<_Np-1, _Rest...> { };
template<typename _First, typename... _Rest>
struct _Nth_type<0, _First, _Rest...>
{ using type = _First; };
} // namespace __variant
} // namespace __detail
#define __cpp_lib_variant 201606L
template<typename... _Types> class tuple;
template<typename... _Types> class variant;
template <typename> struct hash;
template<typename _Variant>
struct variant_size;
template<typename _Variant>
struct variant_size<const _Variant> : variant_size<_Variant> {};
template<typename _Variant>
struct variant_size<volatile _Variant> : variant_size<_Variant> {};
template<typename _Variant>
struct variant_size<const volatile _Variant> : variant_size<_Variant> {};
template<typename... _Types>
struct variant_size<variant<_Types...>>
: std::integral_constant<size_t, sizeof...(_Types)> {};
template<typename _Variant>
inline constexpr size_t variant_size_v = variant_size<_Variant>::value;
template<size_t _Np, typename _Variant>
struct variant_alternative;
template<size_t _Np, typename _First, typename... _Rest>
struct variant_alternative<_Np, variant<_First, _Rest...>>
: variant_alternative<_Np-1, variant<_Rest...>> {};
template<typename _First, typename... _Rest>
struct variant_alternative<0, variant<_First, _Rest...>>
{ using type = _First; };
template<size_t _Np, typename _Variant>
using variant_alternative_t =
typename variant_alternative<_Np, _Variant>::type;
template<size_t _Np, typename _Variant>
struct variant_alternative<_Np, const _Variant>
{ using type = add_const_t<variant_alternative_t<_Np, _Variant>>; };
template<size_t _Np, typename _Variant>
struct variant_alternative<_Np, volatile _Variant>
{ using type = add_volatile_t<variant_alternative_t<_Np, _Variant>>; };
template<size_t _Np, typename _Variant>
struct variant_alternative<_Np, const volatile _Variant>
{ using type = add_cv_t<variant_alternative_t<_Np, _Variant>>; };
inline constexpr size_t variant_npos = -1;
template<size_t _Np, typename... _Types>
constexpr variant_alternative_t<_Np, variant<_Types...>>&
get(variant<_Types...>&);
template<size_t _Np, typename... _Types>
constexpr variant_alternative_t<_Np, variant<_Types...>>&&
get(variant<_Types...>&&);
template<size_t _Np, typename... _Types>
constexpr variant_alternative_t<_Np, variant<_Types...>> const&
get(const variant<_Types...>&);
template<size_t _Np, typename... _Types>
constexpr variant_alternative_t<_Np, variant<_Types...>> const&&
get(const variant<_Types...>&&);
template<typename _Result_type, typename _Visitor, typename... _Variants>
constexpr decltype(auto)
__do_visit(_Visitor&& __visitor, _Variants&&... __variants);
template <typename... _Types, typename _Tp>
decltype(auto)
__variant_cast(_Tp&& __rhs)
{
if constexpr (is_lvalue_reference_v<_Tp>)
{
if constexpr (is_const_v<remove_reference_t<_Tp>>)
return static_cast<const variant<_Types...>&>(__rhs);
else
return static_cast<variant<_Types...>&>(__rhs);
}
else
return static_cast<variant<_Types...>&&>(__rhs);
}
namespace __detail
{
namespace __variant
{
// Returns the first appearance of _Tp in _Types.
// Returns sizeof...(_Types) if _Tp is not in _Types.
template<typename _Tp, typename... _Types>
struct __index_of : std::integral_constant<size_t, 0> {};
template<typename _Tp, typename... _Types>
inline constexpr size_t __index_of_v = __index_of<_Tp, _Types...>::value;
template<typename _Tp, typename _First, typename... _Rest>
struct __index_of<_Tp, _First, _Rest...> :
std::integral_constant<size_t, is_same_v<_Tp, _First>
? 0 : __index_of_v<_Tp, _Rest...> + 1> {};
// used for raw visitation
struct __variant_cookie {};
// used for raw visitation with indices passed in
struct __variant_idx_cookie { using type = __variant_idx_cookie; };
// Used to enable deduction (and same-type checking) for std::visit:
template<typename _Tp> struct __deduce_visit_result { using type = _Tp; };
// Visit variants that might be valueless.
template<typename _Visitor, typename... _Variants>
constexpr void
__raw_visit(_Visitor&& __visitor, _Variants&&... __variants)
{
std::__do_visit<__variant_cookie>(std::forward<_Visitor>(__visitor),
std::forward<_Variants>(__variants)...);
}
// Visit variants that might be valueless, passing indices to the visitor.
template<typename _Visitor, typename... _Variants>
constexpr void
__raw_idx_visit(_Visitor&& __visitor, _Variants&&... __variants)
{
std::__do_visit<__variant_idx_cookie>(std::forward<_Visitor>(__visitor),
std::forward<_Variants>(__variants)...);
}
// _Uninitialized<T> is guaranteed to be a trivially destructible type,
// even if T is not.
template<typename _Type, bool = std::is_trivially_destructible_v<_Type>>
struct _Uninitialized;
template<typename _Type>
struct _Uninitialized<_Type, true>
{
template<typename... _Args>
constexpr
_Uninitialized(in_place_index_t<0>, _Args&&... __args)
: _M_storage(std::forward<_Args>(__args)...)
{ }
constexpr const _Type& _M_get() const & noexcept
{ return _M_storage; }
constexpr _Type& _M_get() & noexcept
{ return _M_storage; }
constexpr const _Type&& _M_get() const && noexcept
{ return std::move(_M_storage); }
constexpr _Type&& _M_get() && noexcept
{ return std::move(_M_storage); }
_Type _M_storage;
};
template<typename _Type>
struct _Uninitialized<_Type, false>
{
template<typename... _Args>
constexpr
_Uninitialized(in_place_index_t<0>, _Args&&... __args)
{
::new ((void*)std::addressof(_M_storage))
_Type(std::forward<_Args>(__args)...);
}
const _Type& _M_get() const & noexcept
{ return *_M_storage._M_ptr(); }
_Type& _M_get() & noexcept
{ return *_M_storage._M_ptr(); }
const _Type&& _M_get() const && noexcept
{ return std::move(*_M_storage._M_ptr()); }
_Type&& _M_get() && noexcept
{ return std::move(*_M_storage._M_ptr()); }
__gnu_cxx::__aligned_membuf<_Type> _M_storage;
};
template<typename _Union>
constexpr decltype(auto)
__get(in_place_index_t<0>, _Union&& __u) noexcept
{ return std::forward<_Union>(__u)._M_first._M_get(); }
template<size_t _Np, typename _Union>
constexpr decltype(auto)
__get(in_place_index_t<_Np>, _Union&& __u) noexcept
{
return __variant::__get(in_place_index<_Np-1>,
std::forward<_Union>(__u)._M_rest);
}
// Returns the typed storage for __v.
template<size_t _Np, typename _Variant>
constexpr decltype(auto)
__get(_Variant&& __v) noexcept
{
return __variant::__get(std::in_place_index<_Np>,
std::forward<_Variant>(__v)._M_u);
}
template<typename... _Types>
struct _Traits
{
static constexpr bool _S_default_ctor =
is_default_constructible_v<typename _Nth_type<0, _Types...>::type>;
static constexpr bool _S_copy_ctor =
(is_copy_constructible_v<_Types> && ...);
static constexpr bool _S_move_ctor =
(is_move_constructible_v<_Types> && ...);
static constexpr bool _S_copy_assign =
_S_copy_ctor
&& (is_copy_assignable_v<_Types> && ...);
static constexpr bool _S_move_assign =
_S_move_ctor
&& (is_move_assignable_v<_Types> && ...);
static constexpr bool _S_trivial_dtor =
(is_trivially_destructible_v<_Types> && ...);
static constexpr bool _S_trivial_copy_ctor =
(is_trivially_copy_constructible_v<_Types> && ...);
static constexpr bool _S_trivial_move_ctor =
(is_trivially_move_constructible_v<_Types> && ...);
static constexpr bool _S_trivial_copy_assign =
_S_trivial_dtor && _S_trivial_copy_ctor
&& (is_trivially_copy_assignable_v<_Types> && ...);
static constexpr bool _S_trivial_move_assign =
_S_trivial_dtor && _S_trivial_move_ctor
&& (is_trivially_move_assignable_v<_Types> && ...);
// The following nothrow traits are for non-trivial SMFs. Trivial SMFs
// are always nothrow.
static constexpr bool _S_nothrow_default_ctor =
is_nothrow_default_constructible_v<
typename _Nth_type<0, _Types...>::type>;
static constexpr bool _S_nothrow_copy_ctor = false;
static constexpr bool _S_nothrow_move_ctor =
(is_nothrow_move_constructible_v<_Types> && ...);
static constexpr bool _S_nothrow_copy_assign = false;
static constexpr bool _S_nothrow_move_assign =
_S_nothrow_move_ctor
&& (is_nothrow_move_assignable_v<_Types> && ...);
};
// Defines members and ctors.
template<typename... _Types>
union _Variadic_union { };
template<typename _First, typename... _Rest>
union _Variadic_union<_First, _Rest...>
{
constexpr _Variadic_union() : _M_rest() { }
template<typename... _Args>
constexpr _Variadic_union(in_place_index_t<0>, _Args&&... __args)
: _M_first(in_place_index<0>, std::forward<_Args>(__args)...)
{ }
template<size_t _Np, typename... _Args>
constexpr _Variadic_union(in_place_index_t<_Np>, _Args&&... __args)
: _M_rest(in_place_index<_Np-1>, std::forward<_Args>(__args)...)
{ }
_Uninitialized<_First> _M_first;
_Variadic_union<_Rest...> _M_rest;
};
// _Never_valueless_alt is true for variant alternatives that can
// always be placed in a variant without it becoming valueless.
// For suitably-small, trivially copyable types we can create temporaries
// on the stack and then memcpy them into place.
template<typename _Tp>
struct _Never_valueless_alt
: __and_<bool_constant<sizeof(_Tp) <= 256>, is_trivially_copyable<_Tp>>
{ };
// Specialize _Never_valueless_alt for other types which have a
// non-throwing and cheap move construction and move assignment operator,
// so that emplacing the type will provide the strong exception-safety
// guarantee, by creating and moving a temporary.
// Whether _Never_valueless_alt<T> is true or not affects the ABI of a
// variant using that alternative, so we can't change the value later!
// True if every alternative in _Types... can be emplaced in a variant
// without it becoming valueless. If this is true, variant<_Types...>
// can never be valueless, which enables some minor optimizations.
template <typename... _Types>
constexpr bool __never_valueless()
{
return _Traits<_Types...>::_S_move_assign
&& (_Never_valueless_alt<_Types>::value && ...);
}
// Defines index and the dtor, possibly trivial.
template<bool __trivially_destructible, typename... _Types>
struct _Variant_storage;
template <typename... _Types>
using __select_index =
typename __select_int::_Select_int_base<sizeof...(_Types),
unsigned char,
unsigned short>::type::value_type;
template<typename... _Types>
struct _Variant_storage<false, _Types...>
{
constexpr
_Variant_storage()
: _M_index(static_cast<__index_type>(variant_npos))
{ }
template<size_t _Np, typename... _Args>
constexpr
_Variant_storage(in_place_index_t<_Np>, _Args&&... __args)
: _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...),
_M_index{_Np}
{ }
void _M_reset()
{
if (!_M_valid()) [[unlikely]]
return;
std::__do_visit<void>([](auto&& __this_mem) mutable
{
std::_Destroy(std::__addressof(__this_mem));
}, __variant_cast<_Types...>(*this));
_M_index = static_cast<__index_type>(variant_npos);
}
~_Variant_storage()
{ _M_reset(); }
void*
_M_storage() const noexcept
{
return const_cast<void*>(static_cast<const void*>(
std::addressof(_M_u)));
}
constexpr bool
_M_valid() const noexcept
{
if constexpr (__variant::__never_valueless<_Types...>())
return true;
return this->_M_index != __index_type(variant_npos);
}
_Variadic_union<_Types...> _M_u;
using __index_type = __select_index<_Types...>;
__index_type _M_index;
};
template<typename... _Types>
struct _Variant_storage<true, _Types...>
{
constexpr
_Variant_storage()
: _M_index(static_cast<__index_type>(variant_npos))
{ }
template<size_t _Np, typename... _Args>
constexpr
_Variant_storage(in_place_index_t<_Np>, _Args&&... __args)
: _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...),
_M_index{_Np}
{ }
void _M_reset() noexcept
{ _M_index = static_cast<__index_type>(variant_npos); }
void*
_M_storage() const noexcept
{
return const_cast<void*>(static_cast<const void*>(
std::addressof(_M_u)));
}
constexpr bool
_M_valid() const noexcept
{
if constexpr (__variant::__never_valueless<_Types...>())
return true;
return this->_M_index != static_cast<__index_type>(variant_npos);
}
_Variadic_union<_Types...> _M_u;
using __index_type = __select_index<_Types...>;
__index_type _M_index;
};
template<typename... _Types>
using _Variant_storage_alias =
_Variant_storage<_Traits<_Types...>::_S_trivial_dtor, _Types...>;
template<typename _Tp, typename _Up>
void __variant_construct_single(_Tp&& __lhs, _Up&& __rhs_mem)
{
void* __storage = std::addressof(__lhs._M_u);
using _Type = remove_reference_t<decltype(__rhs_mem)>;
if constexpr (!is_same_v<_Type, __variant_cookie>)
::new (__storage)
_Type(std::forward<decltype(__rhs_mem)>(__rhs_mem));
}
template<typename... _Types, typename _Tp, typename _Up>
void __variant_construct(_Tp&& __lhs, _Up&& __rhs)
{
__lhs._M_index = __rhs._M_index;
__variant::__raw_visit([&__lhs](auto&& __rhs_mem) mutable
{
__variant_construct_single(std::forward<_Tp>(__lhs),
std::forward<decltype(__rhs_mem)>(__rhs_mem));
}, __variant_cast<_Types...>(std::forward<_Up>(__rhs)));
}
// The following are (Copy|Move) (ctor|assign) layers for forwarding
// triviality and handling non-trivial SMF behaviors.
template<bool, typename... _Types>
struct _Copy_ctor_base : _Variant_storage_alias<_Types...>
{
using _Base = _Variant_storage_alias<_Types...>;
using _Base::_Base;
_Copy_ctor_base(const _Copy_ctor_base& __rhs)
noexcept(_Traits<_Types...>::_S_nothrow_copy_ctor)
{
__variant_construct<_Types...>(*this, __rhs);
}
_Copy_ctor_base(_Copy_ctor_base&&) = default;
_Copy_ctor_base& operator=(const _Copy_ctor_base&) = default;
_Copy_ctor_base& operator=(_Copy_ctor_base&&) = default;
};
template<typename... _Types>
struct _Copy_ctor_base<true, _Types...> : _Variant_storage_alias<_Types...>
{
using _Base = _Variant_storage_alias<_Types...>;
using _Base::_Base;
};
template<typename... _Types>
using _Copy_ctor_alias =
_Copy_ctor_base<_Traits<_Types...>::_S_trivial_copy_ctor, _Types...>;
template<bool, typename... _Types>
struct _Move_ctor_base : _Copy_ctor_alias<_Types...>
{
using _Base = _Copy_ctor_alias<_Types...>;
using _Base::_Base;
_Move_ctor_base(_Move_ctor_base&& __rhs)
noexcept(_Traits<_Types...>::_S_nothrow_move_ctor)
{
__variant_construct<_Types...>(*this, std::move(__rhs));
}
template<typename _Up>
void _M_destructive_move(unsigned short __rhs_index, _Up&& __rhs)
{
this->_M_reset();
__variant_construct_single(*this, std::forward<_Up>(__rhs));
this->_M_index = __rhs_index;
}
template<typename _Up>
void _M_destructive_copy(unsigned short __rhs_index, const _Up& __rhs)
{
this->_M_reset();
__variant_construct_single(*this, __rhs);
this->_M_index = __rhs_index;
}
_Move_ctor_base(const _Move_ctor_base&) = default;
_Move_ctor_base& operator=(const _Move_ctor_base&) = default;
_Move_ctor_base& operator=(_Move_ctor_base&&) = default;
};
template<typename... _Types>
struct _Move_ctor_base<true, _Types...> : _Copy_ctor_alias<_Types...>
{
using _Base = _Copy_ctor_alias<_Types...>;
using _Base::_Base;
template<typename _Up>
void _M_destructive_move(unsigned short __rhs_index, _Up&& __rhs)
{
this->_M_reset();
__variant_construct_single(*this, std::forward<_Up>(__rhs));
this->_M_index = __rhs_index;
}
template<typename _Up>
void _M_destructive_copy(unsigned short __rhs_index, const _Up& __rhs)
{
this->_M_reset();
__variant_construct_single(*this, __rhs);
this->_M_index = __rhs_index;
}
};
template<typename... _Types>
using _Move_ctor_alias =
_Move_ctor_base<_Traits<_Types...>::_S_trivial_move_ctor, _Types...>;
template<bool, typename... _Types>
struct _Copy_assign_base : _Move_ctor_alias<_Types...>
{
using _Base = _Move_ctor_alias<_Types...>;
using _Base::_Base;
_Copy_assign_base&
operator=(const _Copy_assign_base& __rhs)
noexcept(_Traits<_Types...>::_S_nothrow_copy_assign)
{
__variant::__raw_idx_visit(
[this](auto&& __rhs_mem, auto __rhs_index) mutable
{
if constexpr (__rhs_index != variant_npos)
{
if (this->_M_index == __rhs_index)
__variant::__get<__rhs_index>(*this) = __rhs_mem;
else
{
using __rhs_type = __remove_cvref_t<decltype(__rhs_mem)>;
if constexpr (is_nothrow_copy_constructible_v<__rhs_type>
|| !is_nothrow_move_constructible_v<__rhs_type>)
// The standard says this->emplace<__rhs_type>(__rhs_mem)
// should be used here, but _M_destructive_copy is
// equivalent in this case. Either copy construction
// doesn't throw, so _M_destructive_copy gives strong
// exception safety guarantee, or both copy construction
// and move construction can throw, so emplace only gives
// basic exception safety anyway.
this->_M_destructive_copy(__rhs_index, __rhs_mem);
else
__variant_cast<_Types...>(*this)
= variant<_Types...>(std::in_place_index<__rhs_index>,
__rhs_mem);
}
}
else
this->_M_reset();
}, __variant_cast<_Types...>(__rhs));
return *this;
}
_Copy_assign_base(const _Copy_assign_base&) = default;
_Copy_assign_base(_Copy_assign_base&&) = default;
_Copy_assign_base& operator=(_Copy_assign_base&&) = default;
};
template<typename... _Types>
struct _Copy_assign_base<true, _Types...> : _Move_ctor_alias<_Types...>
{
using _Base = _Move_ctor_alias<_Types...>;
using _Base::_Base;
};
template<typename... _Types>
using _Copy_assign_alias =
_Copy_assign_base<_Traits<_Types...>::_S_trivial_copy_assign, _Types...>;
template<bool, typename... _Types>
struct _Move_assign_base : _Copy_assign_alias<_Types...>
{
using _Base = _Copy_assign_alias<_Types...>;
using _Base::_Base;
_Move_assign_base&
operator=(_Move_assign_base&& __rhs)
noexcept(_Traits<_Types...>::_S_nothrow_move_assign)
{
__variant::__raw_idx_visit(
[this](auto&& __rhs_mem, auto __rhs_index) mutable
{
if constexpr (__rhs_index != variant_npos)
{
if (this->_M_index == __rhs_index)
__variant::__get<__rhs_index>(*this) = std::move(__rhs_mem);
else
__variant_cast<_Types...>(*this)
.template emplace<__rhs_index>(std::move(__rhs_mem));
}
else
this->_M_reset();
}, __variant_cast<_Types...>(__rhs));
return *this;
}
_Move_assign_base(const _Move_assign_base&) = default;
_Move_assign_base(_Move_assign_base&&) = default;
_Move_assign_base& operator=(const _Move_assign_base&) = default;
};
template<typename... _Types>
struct _Move_assign_base<true, _Types...> : _Copy_assign_alias<_Types...>
{
using _Base = _Copy_assign_alias<_Types...>;
using _Base::_Base;
};
template<typename... _Types>
using _Move_assign_alias =
_Move_assign_base<_Traits<_Types...>::_S_trivial_move_assign, _Types...>;
template<typename... _Types>
struct _Variant_base : _Move_assign_alias<_Types...>
{
using _Base = _Move_assign_alias<_Types...>;
constexpr
_Variant_base()
noexcept(_Traits<_Types...>::_S_nothrow_default_ctor)
: _Variant_base(in_place_index<0>) { }
template<size_t _Np, typename... _Args>
constexpr explicit
_Variant_base(in_place_index_t<_Np> __i, _Args&&... __args)
: _Base(__i, std::forward<_Args>(__args)...)
{ }
_Variant_base(const _Variant_base&) = default;
_Variant_base(_Variant_base&&) = default;
_Variant_base& operator=(const _Variant_base&) = default;
_Variant_base& operator=(_Variant_base&&) = default;
};
// For how many times does _Tp appear in _Tuple?
template<typename _Tp, typename _Tuple>
struct __tuple_count;
template<typename _Tp, typename _Tuple>
inline constexpr size_t __tuple_count_v =
__tuple_count<_Tp, _Tuple>::value;
template<typename _Tp, typename... _Types>
struct __tuple_count<_Tp, tuple<_Types...>>
: integral_constant<size_t, 0> { };
template<typename _Tp, typename _First, typename... _Rest>
struct __tuple_count<_Tp, tuple<_First, _Rest...>>
: integral_constant<
size_t,
__tuple_count_v<_Tp, tuple<_Rest...>> + is_same_v<_Tp, _First>> { };
// TODO: Reuse this in <tuple> ?
template<typename _Tp, typename... _Types>
inline constexpr bool __exactly_once =
__tuple_count_v<_Tp, tuple<_Types...>> == 1;
// Helper used to check for valid conversions that don't involve narrowing.
template<typename _Ti> struct _Arr { _Ti _M_x[1]; };
// "Build an imaginary function FUN(Ti) for each alternative type Ti"
template<size_t _Ind, typename _Tp, typename _Ti, typename = void>
struct _Build_FUN
{
// This function means 'using _Build_FUN<I, T, Ti>::_S_fun;' is valid,
// but only static functions will be considered in the call below.
void _S_fun();
};
// "... for which Ti x[] = {std::forward<T>(t)}; is well-formed."
template<size_t _Ind, typename _Tp, typename _Ti>
struct _Build_FUN<_Ind, _Tp, _Ti,
void_t<decltype(_Arr<_Ti>{{std::declval<_Tp>()}})>>
{
// This is the FUN function for type _Ti, with index _Ind
static integral_constant<size_t, _Ind> _S_fun(_Ti);
};
template<typename _Tp, typename _Variant,
typename = make_index_sequence<variant_size_v<_Variant>>>
struct _Build_FUNs;
template<typename _Tp, typename... _Ti, size_t... _Ind>
struct _Build_FUNs<_Tp, variant<_Ti...>, index_sequence<_Ind...>>
: _Build_FUN<_Ind, _Tp, _Ti>...
{
using _Build_FUN<_Ind, _Tp, _Ti>::_S_fun...;
};
// The index j of the overload FUN(Tj) selected by overload resolution
// for FUN(std::forward<_Tp>(t))
template<typename _Tp, typename _Variant>
using _FUN_type
= decltype(_Build_FUNs<_Tp, _Variant>::_S_fun(std::declval<_Tp>()));
// The index selected for FUN(std::forward<T>(t)), or variant_npos if none.
template<typename _Tp, typename _Variant, typename = void>
struct __accepted_index
: integral_constant<size_t, variant_npos>
{ };
template<typename _Tp, typename _Variant>
struct __accepted_index<_Tp, _Variant, void_t<_FUN_type<_Tp, _Variant>>>
: _FUN_type<_Tp, _Variant>
{ };
// Returns the raw storage for __v.
template<typename _Variant>
void* __get_storage(_Variant&& __v) noexcept
{ return __v._M_storage(); }
template <typename _Maybe_variant_cookie, typename _Variant>
struct _Extra_visit_slot_needed
{
template <typename> struct _Variant_never_valueless;
template <typename... _Types>
struct _Variant_never_valueless<variant<_Types...>>
: bool_constant<__variant::__never_valueless<_Types...>()> {};
static constexpr bool value =
(is_same_v<_Maybe_variant_cookie, __variant_cookie>
|| is_same_v<_Maybe_variant_cookie, __variant_idx_cookie>)
&& !_Variant_never_valueless<__remove_cvref_t<_Variant>>::value;
};
// Used for storing a multi-dimensional vtable.
template<typename _Tp, size_t... _Dimensions>
struct _Multi_array;
// Partial specialization with rank zero, stores a single _Tp element.
template<typename _Tp>
struct _Multi_array<_Tp>
{
template<typename>
struct __untag_result
: false_type
{ using element_type = _Tp; };
template <typename... _Args>
struct __untag_result<const void(*)(_Args...)>
: false_type
{ using element_type = void(*)(_Args...); };
template <typename... _Args>
struct __untag_result<__variant_cookie(*)(_Args...)>
: false_type
{ using element_type = void(*)(_Args...); };
template <typename... _Args>
struct __untag_result<__variant_idx_cookie(*)(_Args...)>
: false_type
{ using element_type = void(*)(_Args...); };
template <typename _Res, typename... _Args>
struct __untag_result<__deduce_visit_result<_Res>(*)(_Args...)>
: true_type
{ using element_type = _Res(*)(_Args...); };
using __result_is_deduced = __untag_result<_Tp>;
constexpr const typename __untag_result<_Tp>::element_type&
_M_access() const
{ return _M_data; }
typename __untag_result<_Tp>::element_type _M_data;
};
// Partial specialization with rank >= 1.
template<typename _Ret,
typename _Visitor,
typename... _Variants,
size_t __first, size_t... __rest>
struct _Multi_array<_Ret(*)(_Visitor, _Variants...), __first, __rest...>
{
static constexpr size_t __index =
sizeof...(_Variants) - sizeof...(__rest) - 1;
using _Variant = typename _Nth_type<__index, _Variants...>::type;
static constexpr int __do_cookie =
_Extra_visit_slot_needed<_Ret, _Variant>::value ? 1 : 0;
using _Tp = _Ret(*)(_Visitor, _Variants...);
template<typename... _Args>
constexpr decltype(auto)
_M_access(size_t __first_index, _Args... __rest_indices) const
{
return _M_arr[__first_index + __do_cookie]
._M_access(__rest_indices...);
}
_Multi_array<_Tp, __rest...> _M_arr[__first + __do_cookie];
};
// Creates a multi-dimensional vtable recursively.
//
// For example,
// visit([](auto, auto){},
// variant<int, char>(), // typedef'ed as V1
// variant<float, double, long double>()) // typedef'ed as V2
// will trigger instantiations of:
// __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 2, 3>,
// tuple<V1&&, V2&&>, std::index_sequence<>>
// __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>,
// tuple<V1&&, V2&&>, std::index_sequence<0>>
// __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
// tuple<V1&&, V2&&>, std::index_sequence<0, 0>>
// __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
// tuple<V1&&, V2&&>, std::index_sequence<0, 1>>
// __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
// tuple<V1&&, V2&&>, std::index_sequence<0, 2>>
// __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>,
// tuple<V1&&, V2&&>, std::index_sequence<1>>
// __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
// tuple<V1&&, V2&&>, std::index_sequence<1, 0>>
// __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
// tuple<V1&&, V2&&>, std::index_sequence<1, 1>>
// __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
// tuple<V1&&, V2&&>, std::index_sequence<1, 2>>
// The returned multi-dimensional vtable can be fast accessed by the visitor
// using index calculation.
template<typename _Array_type, typename _Index_seq>
struct __gen_vtable_impl;
// Defines the _S_apply() member that returns a _Multi_array populated
// with function pointers that perform the visitation expressions e(m)
// for each valid pack of indexes into the variant types _Variants.
//
// This partial specialization builds up the index sequences by recursively
// calling _S_apply() on the next specialization of __gen_vtable_impl.
// The base case of the recursion defines the actual function pointers.
template<typename _Result_type, typename _Visitor, size_t... __dimensions,
typename... _Variants, size_t... __indices>
struct __gen_vtable_impl<
_Multi_array<_Result_type (*)(_Visitor, _Variants...), __dimensions...>,
std::index_sequence<__indices...>>
{
using _Next =
remove_reference_t<typename _Nth_type<sizeof...(__indices),
_Variants...>::type>;
using _Array_type =
_Multi_array<_Result_type (*)(_Visitor, _Variants...),
__dimensions...>;
static constexpr _Array_type
_S_apply()
{
_Array_type __vtable{};
_S_apply_all_alts(
__vtable, make_index_sequence<variant_size_v<_Next>>());
return __vtable;
}
template<size_t... __var_indices>
static constexpr void
_S_apply_all_alts(_Array_type& __vtable,
std::index_sequence<__var_indices...>)
{
if constexpr (_Extra_visit_slot_needed<_Result_type, _Next>::value)
(_S_apply_single_alt<true, __var_indices>(
__vtable._M_arr[__var_indices + 1],
&(__vtable._M_arr[0])), ...);
else
(_S_apply_single_alt<false, __var_indices>(
__vtable._M_arr[__var_indices]), ...);
}
template<bool __do_cookie, size_t __index, typename _Tp>
static constexpr void
_S_apply_single_alt(_Tp& __element, _Tp* __cookie_element = nullptr)
{
if constexpr (__do_cookie)
{
__element = __gen_vtable_impl<
_Tp,
std::index_sequence<__indices..., __index>>::_S_apply();
*__cookie_element = __gen_vtable_impl<
_Tp,
std::index_sequence<__indices..., variant_npos>>::_S_apply();
}
else
{
auto __tmp_element = __gen_vtable_impl<
remove_reference_t<decltype(__element)>,
std::index_sequence<__indices..., __index>>::_S_apply();
static_assert(is_same_v<_Tp, decltype(__tmp_element)>,
"std::visit requires the visitor to have the same "
"return type for all alternatives of a variant");
__element = __tmp_element;
}
}
};
// This partial specialization is the base case for the recursion.
// It populates a _Multi_array element with the address of a function
// that invokes the visitor with the alternatives specified by __indices.
template<typename _Result_type, typename _Visitor, typename... _Variants,
size_t... __indices>
struct __gen_vtable_impl<
_Multi_array<_Result_type (*)(_Visitor, _Variants...)>,
std::index_sequence<__indices...>>
{
using _Array_type =
_Multi_array<_Result_type (*)(_Visitor, _Variants...)>;
template<size_t __index, typename _Variant>
static constexpr decltype(auto)
__element_by_index_or_cookie(_Variant&& __var) noexcept
{
if constexpr (__index != variant_npos)
return __variant::__get<__index>(std::forward<_Variant>(__var));
else
return __variant_cookie{};
}
static constexpr decltype(auto)
__visit_invoke(_Visitor&& __visitor, _Variants... __vars)
{
if constexpr (is_same_v<_Result_type, __variant_idx_cookie>)
// For raw visitation using indices, pass the indices to the visitor
// and discard the return value:
std::__invoke(std::forward<_Visitor>(__visitor),
__element_by_index_or_cookie<__indices>(
std::forward<_Variants>(__vars))...,
integral_constant<size_t, __indices>()...);
else if constexpr (is_same_v<_Result_type, __variant_cookie>)
// For raw visitation without indices, and discard the return value:
std::__invoke(std::forward<_Visitor>(__visitor),
__element_by_index_or_cookie<__indices>(
std::forward<_Variants>(__vars))...);
else if constexpr (_Array_type::__result_is_deduced::value)
// For the usual std::visit case deduce the return value:
return std::__invoke(std::forward<_Visitor>(__visitor),
__element_by_index_or_cookie<__indices>(
std::forward<_Variants>(__vars))...);
else // for std::visit<R> use INVOKE<R>
return std::__invoke_r<_Result_type>(
std::forward<_Visitor>(__visitor),
__variant::__get<__indices>(std::forward<_Variants>(__vars))...);
}
static constexpr auto
_S_apply()
{
if constexpr (_Array_type::__result_is_deduced::value)
{
constexpr bool __visit_ret_type_mismatch =
!is_same_v<typename _Result_type::type,
decltype(__visit_invoke(std::declval<_Visitor>(),
std::declval<_Variants>()...))>;
if constexpr (__visit_ret_type_mismatch)
{
struct __cannot_match {};
return __cannot_match{};
}
else
return _Array_type{&__visit_invoke};
}
else
return _Array_type{&__visit_invoke};
}
};
template<typename _Result_type, typename _Visitor, typename... _Variants>
struct __gen_vtable
{
using _Array_type =
_Multi_array<_Result_type (*)(_Visitor, _Variants...),
variant_size_v<remove_reference_t<_Variants>>...>;
static constexpr _Array_type _S_vtable
= __gen_vtable_impl<_Array_type, std::index_sequence<>>::_S_apply();
};
template<size_t _Np, typename _Tp>
struct _Base_dedup : public _Tp { };
template<typename _Variant, typename __indices>
struct _Variant_hash_base;
template<typename... _Types, size_t... __indices>
struct _Variant_hash_base<variant<_Types...>,
std::index_sequence<__indices...>>
: _Base_dedup<__indices, __poison_hash<remove_const_t<_Types>>>... { };
template<size_t _Np, typename _Variant>
using __get_t = decltype(std::get<_Np>(std::declval<_Variant>()));
// Return type of std::visit.
template<typename _Visitor, typename... _Variants>
using __visit_result_t
= invoke_result_t<_Visitor, __get_t<0, _Variants>...>;
template<typename _Tp, typename... _Types>
constexpr inline bool __same_types = (is_same_v<_Tp, _Types> && ...);
template <typename _Visitor, typename _Variant, size_t... _Idxs>
constexpr bool __check_visitor_results(std::index_sequence<_Idxs...>)
{
return __same_types<
invoke_result_t<_Visitor, __get_t<_Idxs, _Variant>>...
>;
}
} // namespace __variant
} // namespace __detail
template<size_t _Np, typename _Variant, typename... _Args>
void __variant_construct_by_index(_Variant& __v, _Args&&... __args)
{
__v._M_index = _Np;
auto&& __storage = __detail::__variant::__get<_Np>(__v);
::new ((void*)std::addressof(__storage))
remove_reference_t<decltype(__storage)>
(std::forward<_Args>(__args)...);
}
template<typename _Tp, typename... _Types>
constexpr bool
holds_alternative(const variant<_Types...>& __v) noexcept
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T must occur exactly once in alternatives");
return __v.index() == __detail::__variant::__index_of_v<_Tp, _Types...>;
}
template<typename _Tp, typename... _Types>
constexpr _Tp& get(variant<_Types...>& __v)
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T must occur exactly once in alternatives");
static_assert(!is_void_v<_Tp>, "_Tp must not be void");
return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v);
}
template<typename _Tp, typename... _Types>
constexpr _Tp&& get(variant<_Types...>&& __v)
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T must occur exactly once in alternatives");
static_assert(!is_void_v<_Tp>, "_Tp must not be void");
return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(
std::move(__v));
}
template<typename _Tp, typename... _Types>
constexpr const _Tp& get(const variant<_Types...>& __v)
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T must occur exactly once in alternatives");
static_assert(!is_void_v<_Tp>, "_Tp must not be void");
return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v);
}
template<typename _Tp, typename... _Types>
constexpr const _Tp&& get(const variant<_Types...>&& __v)
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T must occur exactly once in alternatives");
static_assert(!is_void_v<_Tp>, "_Tp must not be void");
return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(
std::move(__v));
}
template<size_t _Np, typename... _Types>
constexpr add_pointer_t<variant_alternative_t<_Np, variant<_Types...>>>
get_if(variant<_Types...>* __ptr) noexcept
{
using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>;
static_assert(_Np < sizeof...(_Types),
"The index must be in [0, number of alternatives)");
static_assert(!is_void_v<_Alternative_type>, "_Tp must not be void");
if (__ptr && __ptr->index() == _Np)
return std::addressof(__detail::__variant::__get<_Np>(*__ptr));
return nullptr;
}
template<size_t _Np, typename... _Types>
constexpr
add_pointer_t<const variant_alternative_t<_Np, variant<_Types...>>>
get_if(const variant<_Types...>* __ptr) noexcept
{
using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>;
static_assert(_Np < sizeof...(_Types),
"The index must be in [0, number of alternatives)");
static_assert(!is_void_v<_Alternative_type>, "_Tp must not be void");
if (__ptr && __ptr->index() == _Np)
return std::addressof(__detail::__variant::__get<_Np>(*__ptr));
return nullptr;
}
template<typename _Tp, typename... _Types>
constexpr add_pointer_t<_Tp>
get_if(variant<_Types...>* __ptr) noexcept
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T must occur exactly once in alternatives");
static_assert(!is_void_v<_Tp>, "_Tp must not be void");
return std::get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>(
__ptr);
}
template<typename _Tp, typename... _Types>
constexpr add_pointer_t<const _Tp>
get_if(const variant<_Types...>* __ptr) noexcept
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T must occur exactly once in alternatives");
static_assert(!is_void_v<_Tp>, "_Tp must not be void");
return std::get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>(
__ptr);
}
struct monostate { };
#define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP, __NAME) \
template<typename... _Types> \
constexpr bool operator __OP(const variant<_Types...>& __lhs, \
const variant<_Types...>& __rhs) \
{ \
bool __ret = true; \
__detail::__variant::__raw_idx_visit( \
[&__ret, &__lhs] (auto&& __rhs_mem, auto __rhs_index) mutable \
{ \
if constexpr (__rhs_index != variant_npos) \
{ \
if (__lhs.index() == __rhs_index) \
{ \
auto& __this_mem = std::get<__rhs_index>(__lhs); \
__ret = __this_mem __OP __rhs_mem; \
} \
else \
__ret = (__lhs.index() + 1) __OP (__rhs_index + 1); \
} \
else \
__ret = (__lhs.index() + 1) __OP (__rhs_index + 1); \
}, __rhs); \
return __ret; \
}
_VARIANT_RELATION_FUNCTION_TEMPLATE(<, less)
_VARIANT_RELATION_FUNCTION_TEMPLATE(<=, less_equal)
_VARIANT_RELATION_FUNCTION_TEMPLATE(==, equal)
_VARIANT_RELATION_FUNCTION_TEMPLATE(!=, not_equal)
_VARIANT_RELATION_FUNCTION_TEMPLATE(>=, greater_equal)
_VARIANT_RELATION_FUNCTION_TEMPLATE(>, greater)
#undef _VARIANT_RELATION_FUNCTION_TEMPLATE
constexpr bool operator==(monostate, monostate) noexcept { return true; }
#ifdef __cpp_lib_three_way_comparison
template<typename... _Types>
requires (three_way_comparable<_Types> && ...)
constexpr
common_comparison_category_t<compare_three_way_result_t<_Types>...>
operator<=>(const variant<_Types...>& __v, const variant<_Types...>& __w)
{
common_comparison_category_t<compare_three_way_result_t<_Types>...> __ret
= strong_ordering::equal;
__detail::__variant::__raw_idx_visit(
[&__ret, &__v] (auto&& __w_mem, auto __w_index) mutable
{
if constexpr (__w_index != variant_npos)
{
if (__v.index() == __w_index)
{
auto& __this_mem = std::get<__w_index>(__v);
__ret = __this_mem <=> __w_mem;
return;
}
}
__ret = (__v.index() + 1) <=> (__w_index + 1);
}, __w);
return __ret;
}
constexpr strong_ordering
operator<=>(monostate, monostate) noexcept { return strong_ordering::equal; }
#else
constexpr bool operator!=(monostate, monostate) noexcept { return false; }
constexpr bool operator<(monostate, monostate) noexcept { return false; }
constexpr bool operator>(monostate, monostate) noexcept { return false; }
constexpr bool operator<=(monostate, monostate) noexcept { return true; }
constexpr bool operator>=(monostate, monostate) noexcept { return true; }
#endif
template<typename _Visitor, typename... _Variants>
constexpr __detail::__variant::__visit_result_t<_Visitor, _Variants...>
visit(_Visitor&&, _Variants&&...);
template<typename... _Types>
inline enable_if_t<(is_move_constructible_v<_Types> && ...)
&& (is_swappable_v<_Types> && ...)>
swap(variant<_Types...>& __lhs, variant<_Types...>& __rhs)
noexcept(noexcept(__lhs.swap(__rhs)))
{ __lhs.swap(__rhs); }
template<typename... _Types>
enable_if_t<!((is_move_constructible_v<_Types> && ...)
&& (is_swappable_v<_Types> && ...))>
swap(variant<_Types...>&, variant<_Types...>&) = delete;
class bad_variant_access : public exception
{
public:
bad_variant_access() noexcept { }
const char* what() const noexcept override
{ return _M_reason; }
private:
bad_variant_access(const char* __reason) noexcept : _M_reason(__reason) { }
// Must point to a string with static storage duration:
const char* _M_reason = "bad variant access";
friend void __throw_bad_variant_access(const char* __what);
};
// Must only be called with a string literal
inline void
__throw_bad_variant_access(const char* __what)
{ _GLIBCXX_THROW_OR_ABORT(bad_variant_access(__what)); }
inline void
__throw_bad_variant_access(bool __valueless)
{
if (__valueless) [[__unlikely__]]
__throw_bad_variant_access("std::get: variant is valueless");
else
__throw_bad_variant_access("std::get: wrong index for variant");
}
template<typename... _Types>
class variant
: private __detail::__variant::_Variant_base<_Types...>,
private _Enable_default_constructor<
__detail::__variant::_Traits<_Types...>::_S_default_ctor,
variant<_Types...>>,
private _Enable_copy_move<
__detail::__variant::_Traits<_Types...>::_S_copy_ctor,
__detail::__variant::_Traits<_Types...>::_S_copy_assign,
__detail::__variant::_Traits<_Types...>::_S_move_ctor,
__detail::__variant::_Traits<_Types...>::_S_move_assign,
variant<_Types...>>
{
private:
template <typename... _UTypes, typename _Tp>
friend decltype(auto) __variant_cast(_Tp&&);
template<size_t _Np, typename _Variant, typename... _Args>
friend void __variant_construct_by_index(_Variant& __v,
_Args&&... __args);
static_assert(sizeof...(_Types) > 0,
"variant must have at least one alternative");
static_assert(!(std::is_reference_v<_Types> || ...),
"variant must have no reference alternative");
static_assert(!(std::is_void_v<_Types> || ...),
"variant must have no void alternative");
using _Base = __detail::__variant::_Variant_base<_Types...>;
using _Default_ctor_enabler =
_Enable_default_constructor<
__detail::__variant::_Traits<_Types...>::_S_default_ctor,
variant<_Types...>>;
template<typename _Tp>
static constexpr bool __not_self
= !is_same_v<__remove_cvref_t<_Tp>, variant>;
template<typename _Tp>
static constexpr bool
__exactly_once = __detail::__variant::__exactly_once<_Tp, _Types...>;
template<typename _Tp>
static constexpr size_t __accepted_index
= __detail::__variant::__accepted_index<_Tp, variant>::value;
template<size_t _Np, typename = enable_if_t<(_Np < sizeof...(_Types))>>
using __to_type = variant_alternative_t<_Np, variant>;
template<typename _Tp, typename = enable_if_t<__not_self<_Tp>>>
using __accepted_type = __to_type<__accepted_index<_Tp>>;
template<typename _Tp>
static constexpr size_t __index_of =
__detail::__variant::__index_of_v<_Tp, _Types...>;
using _Traits = __detail::__variant::_Traits<_Types...>;
template<typename _Tp>
struct __is_in_place_tag : false_type { };
template<typename _Tp>
struct __is_in_place_tag<in_place_type_t<_Tp>> : true_type { };
template<size_t _Np>
struct __is_in_place_tag<in_place_index_t<_Np>> : true_type { };
template<typename _Tp>
static constexpr bool __not_in_place_tag
= !__is_in_place_tag<__remove_cvref_t<_Tp>>::value;
public:
variant() = default;
variant(const variant& __rhs) = default;
variant(variant&&) = default;
variant& operator=(const variant&) = default;
variant& operator=(variant&&) = default;
~variant() = default;
template<typename _Tp,
typename = enable_if_t<sizeof...(_Types) != 0>,
typename = enable_if_t<__not_in_place_tag<_Tp>>,
typename _Tj = __accepted_type<_Tp&&>,
typename = enable_if_t<__exactly_once<_Tj>
&& is_constructible_v<_Tj, _Tp>>>
constexpr
variant(_Tp&& __t)
noexcept(is_nothrow_constructible_v<_Tj, _Tp>)
: variant(in_place_index<__accepted_index<_Tp>>,
std::forward<_Tp>(__t))
{ }
template<typename _Tp, typename... _Args,
typename = enable_if_t<__exactly_once<_Tp>
&& is_constructible_v<_Tp, _Args...>>>
constexpr explicit
variant(in_place_type_t<_Tp>, _Args&&... __args)
: variant(in_place_index<__index_of<_Tp>>,
std::forward<_Args>(__args)...)
{ }
template<typename _Tp, typename _Up, typename... _Args,
typename = enable_if_t<__exactly_once<_Tp>
&& is_constructible_v<_Tp,
initializer_list<_Up>&, _Args...>>>
constexpr explicit
variant(in_place_type_t<_Tp>, initializer_list<_Up> __il,
_Args&&... __args)
: variant(in_place_index<__index_of<_Tp>>, __il,
std::forward<_Args>(__args)...)
{ }
template<size_t _Np, typename... _Args,
typename _Tp = __to_type<_Np>,
typename = enable_if_t<is_constructible_v<_Tp, _Args...>>>
constexpr explicit
variant(in_place_index_t<_Np>, _Args&&... __args)
: _Base(in_place_index<_Np>, std::forward<_Args>(__args)...),
_Default_ctor_enabler(_Enable_default_constructor_tag{})
{ }
template<size_t _Np, typename _Up, typename... _Args,
typename _Tp = __to_type<_Np>,
typename = enable_if_t<is_constructible_v<_Tp,
initializer_list<_Up>&,
_Args...>>>
constexpr explicit
variant(in_place_index_t<_Np>, initializer_list<_Up> __il,
_Args&&... __args)
: _Base(in_place_index<_Np>, __il, std::forward<_Args>(__args)...),
_Default_ctor_enabler(_Enable_default_constructor_tag{})
{ }
template<typename _Tp>
enable_if_t<__exactly_once<__accepted_type<_Tp&&>>
&& is_constructible_v<__accepted_type<_Tp&&>, _Tp>
&& is_assignable_v<__accepted_type<_Tp&&>&, _Tp>,
variant&>
operator=(_Tp&& __rhs)
noexcept(is_nothrow_assignable_v<__accepted_type<_Tp&&>&, _Tp>
&& is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp>)
{
constexpr auto __index = __accepted_index<_Tp>;
if (index() == __index)
std::get<__index>(*this) = std::forward<_Tp>(__rhs);
else
{
using _Tj = __accepted_type<_Tp&&>;
if constexpr (is_nothrow_constructible_v<_Tj, _Tp>
|| !is_nothrow_move_constructible_v<_Tj>)
this->emplace<__index>(std::forward<_Tp>(__rhs));
else
operator=(variant(std::forward<_Tp>(__rhs)));
}
return *this;
}
template<typename _Tp, typename... _Args>
enable_if_t<is_constructible_v<_Tp, _Args...> && __exactly_once<_Tp>,
_Tp&>
emplace(_Args&&... __args)
{
constexpr size_t __index = __index_of<_Tp>;
return this->emplace<__index>(std::forward<_Args>(__args)...);
}
template<typename _Tp, typename _Up, typename... _Args>
enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>
&& __exactly_once<_Tp>,
_Tp&>
emplace(initializer_list<_Up> __il, _Args&&... __args)
{
constexpr size_t __index = __index_of<_Tp>;
return this->emplace<__index>(__il, std::forward<_Args>(__args)...);
}
template<size_t _Np, typename... _Args>
enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>,
_Args...>,
variant_alternative_t<_Np, variant>&>
emplace(_Args&&... __args)
{
static_assert(_Np < sizeof...(_Types),
"The index must be in [0, number of alternatives)");
using type = variant_alternative_t<_Np, variant>;
// Provide the strong exception-safety guarantee when possible,
// to avoid becoming valueless.
if constexpr (is_nothrow_constructible_v<type, _Args...>)
{
this->_M_reset();
__variant_construct_by_index<_Np>(*this,
std::forward<_Args>(__args)...);
}
else if constexpr (is_scalar_v<type>)
{
// This might invoke a potentially-throwing conversion operator:
const type __tmp(std::forward<_Args>(__args)...);
// But these steps won't throw:
this->_M_reset();
__variant_construct_by_index<_Np>(*this, __tmp);
}
else if constexpr (__detail::__variant::_Never_valueless_alt<type>()
&& _Traits::_S_move_assign)
{
// This construction might throw:
variant __tmp(in_place_index<_Np>,
std::forward<_Args>(__args)...);
// But _Never_valueless_alt<type> means this won't:
*this = std::move(__tmp);
}
else
{
// This case only provides the basic exception-safety guarantee,
// i.e. the variant can become valueless.
this->_M_reset();
__try
{
__variant_construct_by_index<_Np>(*this,
std::forward<_Args>(__args)...);
}
__catch (...)
{
using __index_type = decltype(this->_M_index);
this->_M_index = static_cast<__index_type>(variant_npos);
__throw_exception_again;
}
}
return std::get<_Np>(*this);
}
template<size_t _Np, typename _Up, typename... _Args>
enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>,
initializer_list<_Up>&, _Args...>,
variant_alternative_t<_Np, variant>&>
emplace(initializer_list<_Up> __il, _Args&&... __args)
{
static_assert(_Np < sizeof...(_Types),
"The index must be in [0, number of alternatives)");
using type = variant_alternative_t<_Np, variant>;
// Provide the strong exception-safety guarantee when possible,
// to avoid becoming valueless.
if constexpr (is_nothrow_constructible_v<type,
initializer_list<_Up>&,
_Args...>)
{
this->_M_reset();
__variant_construct_by_index<_Np>(*this, __il,
std::forward<_Args>(__args)...);
}
else if constexpr (__detail::__variant::_Never_valueless_alt<type>()
&& _Traits::_S_move_assign)
{
// This construction might throw:
variant __tmp(in_place_index<_Np>, __il,
std::forward<_Args>(__args)...);
// But _Never_valueless_alt<type> means this won't:
*this = std::move(__tmp);
}
else
{
// This case only provides the basic exception-safety guarantee,
// i.e. the variant can become valueless.
this->_M_reset();
__try
{
__variant_construct_by_index<_Np>(*this, __il,
std::forward<_Args>(__args)...);
}
__catch (...)
{
using __index_type = decltype(this->_M_index);
this->_M_index = static_cast<__index_type>(variant_npos);
__throw_exception_again;
}
}
return std::get<_Np>(*this);
}
constexpr bool valueless_by_exception() const noexcept
{ return !this->_M_valid(); }
constexpr size_t index() const noexcept
{
using __index_type = typename _Base::__index_type;
if constexpr (__detail::__variant::__never_valueless<_Types...>())
return this->_M_index;
else if constexpr (sizeof...(_Types) <= __index_type(-1) / 2)
return make_signed_t<__index_type>(this->_M_index);
else
return size_t(__index_type(this->_M_index + 1)) - 1;
}
void
swap(variant& __rhs)
noexcept((__is_nothrow_swappable<_Types>::value && ...)
&& is_nothrow_move_constructible_v<variant>)
{
__detail::__variant::__raw_idx_visit(
[this, &__rhs](auto&& __rhs_mem, auto __rhs_index) mutable
{
if constexpr (__rhs_index != variant_npos)
{
if (this->index() == __rhs_index)
{
auto& __this_mem =
std::get<__rhs_index>(*this);
using std::swap;
swap(__this_mem, __rhs_mem);
}
else
{
if (!this->valueless_by_exception()) [[__likely__]]
{
auto __tmp(std::move(__rhs_mem));
__rhs = std::move(*this);
this->_M_destructive_move(__rhs_index,
std::move(__tmp));
}
else
{
this->_M_destructive_move(__rhs_index,
std::move(__rhs_mem));
__rhs._M_reset();
}
}
}
else
{
if (!this->valueless_by_exception()) [[__likely__]]
{
__rhs = std::move(*this);
this->_M_reset();
}
}
}, __rhs);
}
private:
#if defined(__clang__) && __clang_major__ <= 7
public:
using _Base::_M_u; // See https://bugs.llvm.org/show_bug.cgi?id=31852
private:
#endif
template<size_t _Np, typename _Vp>
friend constexpr decltype(auto)
__detail::__variant::__get(_Vp&& __v) noexcept;
template<typename _Vp>
friend void*
__detail::__variant::__get_storage(_Vp&& __v) noexcept;
#define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP) \
template<typename... _Tp> \
friend constexpr bool \
operator __OP(const variant<_Tp...>& __lhs, \
const variant<_Tp...>& __rhs);
_VARIANT_RELATION_FUNCTION_TEMPLATE(<)
_VARIANT_RELATION_FUNCTION_TEMPLATE(<=)
_VARIANT_RELATION_FUNCTION_TEMPLATE(==)
_VARIANT_RELATION_FUNCTION_TEMPLATE(!=)
_VARIANT_RELATION_FUNCTION_TEMPLATE(>=)
_VARIANT_RELATION_FUNCTION_TEMPLATE(>)
#undef _VARIANT_RELATION_FUNCTION_TEMPLATE
};
template<size_t _Np, typename... _Types>
constexpr variant_alternative_t<_Np, variant<_Types...>>&
get(variant<_Types...>& __v)
{
static_assert(_Np < sizeof...(_Types),
"The index must be in [0, number of alternatives)");
if (__v.index() != _Np)
__throw_bad_variant_access(__v.valueless_by_exception());
return __detail::__variant::__get<_Np>(__v);
}
template<size_t _Np, typename... _Types>
constexpr variant_alternative_t<_Np, variant<_Types...>>&&
get(variant<_Types...>&& __v)
{
static_assert(_Np < sizeof...(_Types),
"The index must be in [0, number of alternatives)");
if (__v.index() != _Np)
__throw_bad_variant_access(__v.valueless_by_exception());
return __detail::__variant::__get<_Np>(std::move(__v));
}
template<size_t _Np, typename... _Types>
constexpr const variant_alternative_t<_Np, variant<_Types...>>&
get(const variant<_Types...>& __v)
{
static_assert(_Np < sizeof...(_Types),
"The index must be in [0, number of alternatives)");
if (__v.index() != _Np)
__throw_bad_variant_access(__v.valueless_by_exception());
return __detail::__variant::__get<_Np>(__v);
}
template<size_t _Np, typename... _Types>
constexpr const variant_alternative_t<_Np, variant<_Types...>>&&
get(const variant<_Types...>&& __v)
{
static_assert(_Np < sizeof...(_Types),
"The index must be in [0, number of alternatives)");
if (__v.index() != _Np)
__throw_bad_variant_access(__v.valueless_by_exception());
return __detail::__variant::__get<_Np>(std::move(__v));
}
/// @cond undocumented
template<typename _Result_type, typename _Visitor, typename... _Variants>
constexpr decltype(auto)
__do_visit(_Visitor&& __visitor, _Variants&&... __variants)
{
constexpr auto& __vtable = __detail::__variant::__gen_vtable<
_Result_type, _Visitor&&, _Variants&&...>::_S_vtable;
auto __func_ptr = __vtable._M_access(__variants.index()...);
return (*__func_ptr)(std::forward<_Visitor>(__visitor),
std::forward<_Variants>(__variants)...);
}
/// @endcond
template<typename _Visitor, typename... _Variants>
constexpr __detail::__variant::__visit_result_t<_Visitor, _Variants...>
visit(_Visitor&& __visitor, _Variants&&... __variants)
{
if ((__variants.valueless_by_exception() || ...))
__throw_bad_variant_access("std::visit: variant is valueless");
using _Result_type
= __detail::__variant::__visit_result_t<_Visitor, _Variants...>;
using _Tag = __detail::__variant::__deduce_visit_result<_Result_type>;
if constexpr (sizeof...(_Variants) == 1)
{
constexpr bool __visit_rettypes_match = __detail::__variant::
__check_visitor_results<_Visitor, _Variants...>(
std::make_index_sequence<
std::variant_size<remove_reference_t<_Variants>...>::value>());
if constexpr (!__visit_rettypes_match)
{
static_assert(__visit_rettypes_match,
"std::visit requires the visitor to have the same "
"return type for all alternatives of a variant");
return;
}
else
return std::__do_visit<_Tag>(
std::forward<_Visitor>(__visitor),
std::forward<_Variants>(__variants)...);
}
else
return std::__do_visit<_Tag>(
std::forward<_Visitor>(__visitor),
std::forward<_Variants>(__variants)...);
}
#if __cplusplus > 201703L
template<typename _Res, typename _Visitor, typename... _Variants>
constexpr _Res
visit(_Visitor&& __visitor, _Variants&&... __variants)
{
if ((__variants.valueless_by_exception() || ...))
__throw_bad_variant_access("std::visit<R>: variant is valueless");
return std::__do_visit<_Res>(std::forward<_Visitor>(__visitor),
std::forward<_Variants>(__variants)...);
}
#endif
/// @cond undocumented
template<bool, typename... _Types>
struct __variant_hash_call_base_impl
{
size_t
operator()(const variant<_Types...>& __t) const
noexcept((is_nothrow_invocable_v<hash<decay_t<_Types>>, _Types> && ...))
{
size_t __ret;
__detail::__variant::__raw_visit(
[&__t, &__ret](auto&& __t_mem) mutable
{
using _Type = __remove_cvref_t<decltype(__t_mem)>;
if constexpr (!is_same_v<_Type,
__detail::__variant::__variant_cookie>)
__ret = std::hash<size_t>{}(__t.index())
+ std::hash<_Type>{}(__t_mem);
else
__ret = std::hash<size_t>{}(__t.index());
}, __t);
return __ret;
}
};
template<typename... _Types>
struct __variant_hash_call_base_impl<false, _Types...> {};
template<typename... _Types>
using __variant_hash_call_base =
__variant_hash_call_base_impl<(__poison_hash<remove_const_t<_Types>>::
__enable_hash_call &&...), _Types...>;
/// @endcond
template<typename... _Types>
struct hash<variant<_Types...>>
: private __detail::__variant::_Variant_hash_base<
variant<_Types...>, std::index_sequence_for<_Types...>>,
public __variant_hash_call_base<_Types...>
{
using result_type [[__deprecated__]] = size_t;
using argument_type [[__deprecated__]] = variant<_Types...>;
};
template<>
struct hash<monostate>
{
using result_type [[__deprecated__]] = size_t;
using argument_type [[__deprecated__]] = monostate;
size_t
operator()(const monostate&) const noexcept
{
constexpr size_t __magic_monostate_hash = -7777;
return __magic_monostate_hash;
}
};
template<typename... _Types>
struct __is_fast_hash<hash<variant<_Types...>>>
: bool_constant<(__is_fast_hash<_Types>::value && ...)>
{ };
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif // C++17
#endif // _GLIBCXX_VARIANT