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gcc/libstdc++-v3/include/std/variant
Barrett Adair 258ee761eb Use fold expressions to reduce std::variant instantiation depth 
2017-01-06  Barrett Adair  <barrettellisadair@gmail.com>
	    Jonathan Wakely  <jwakely@redhat.com>

	* include/std/variant (variant, swap): Replace __and_ usage with fold
	expressions.

Co-Authored-By: Jonathan Wakely <jwakely@redhat.com>

From-SVN: r244163
2017-01-06 15:27:01 +00:00

1302 lines
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// <variant> -*- C++ -*-
// Copyright (C) 2016-2017 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 <= 201402L
# include <bits/c++17_warning.h>
#else
#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>
namespace std _GLIBCXX_VISIBILITY(default)
{
namespace __detail
{
namespace __variant
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
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; };
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace __variant
} // namespace __detail
_GLIBCXX_BEGIN_NAMESPACE_VERSION
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>
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>>; };
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...>&&);
_GLIBCXX_END_NAMESPACE_VERSION
namespace __detail
{
namespace __variant
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
// Returns the first apparence 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>
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> {};
// _Uninitialized<T> is guaranteed to be a literal type, even if T is not.
// We have to do this, because [basic.types]p10.5.3 (n4606) is not implemented
// yet. When it's implemented, _Uninitialized<T> can be changed to the alias
// to T, therefore equivalent to being removed entirely.
//
// Another reason we may not want to remove _Uninitialzied<T> may be that, we
// want _Uninitialized<T> to be trivially destructible, no matter whether T
// is; but we will see.
template<typename _Type, bool = std::is_literal_type_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 &
{ return _M_storage; }
constexpr _Type& _M_get() &
{ return _M_storage; }
constexpr const _Type&& _M_get() const &&
{ return std::move(_M_storage); }
constexpr _Type&& _M_get() &&
{ 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 (&_M_storage) _Type(std::forward<_Args>(__args)...); }
const _Type& _M_get() const &
{ return *_M_storage._M_ptr(); }
_Type& _M_get() &
{ return *_M_storage._M_ptr(); }
const _Type&& _M_get() const &&
{ return std::move(*_M_storage._M_ptr()); }
_Type&& _M_get() &&
{ return std::move(*_M_storage._M_ptr()); }
__gnu_cxx::__aligned_membuf<_Type> _M_storage;
};
template<typename _Ref>
_Ref __ref_cast(void* __ptr)
{
return static_cast<_Ref>(*static_cast<remove_reference_t<_Ref>*>(__ptr));
}
template<typename _Union>
constexpr decltype(auto) __get(in_place_index_t<0>, _Union&& __u)
{ 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)
{ return __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)
{
return __get(std::in_place_index<_Np>, std::forward<_Variant>(__v)._M_u);
}
// Various functions as "vtable" entries, where those vtables are used by
// polymorphic operations.
template<typename _Lhs, typename _Rhs>
constexpr void
__erased_ctor(void* __lhs, void* __rhs)
{ ::new (__lhs) remove_reference_t<_Lhs>(__ref_cast<_Rhs>(__rhs)); }
template<typename _Variant, size_t _Np>
constexpr void
__erased_dtor(_Variant&& __v)
{
auto&& __element = __get<_Np>(std::forward<_Variant>(__v));
using _Type = std::remove_reference_t<decltype(__element)>;
__element.~_Type();
}
template<typename _Lhs, typename _Rhs>
constexpr void
__erased_assign(void* __lhs, void* __rhs)
{ __ref_cast<_Lhs>(__lhs) = __ref_cast<_Rhs>(__rhs); }
template<typename _Lhs, typename _Rhs>
constexpr void
__erased_swap(void* __lhs, void* __rhs)
{
using std::swap;
swap(__ref_cast<_Lhs>(__lhs), __ref_cast<_Rhs>(__rhs));
}
template<typename _Variant, size_t _Np>
constexpr bool
__erased_equal_to(_Variant&& __lhs, _Variant&& __rhs)
{
return __get<_Np>(std::forward<_Variant>(__lhs))
== __get<_Np>(std::forward<_Variant>(__rhs));
}
template<typename _Variant, size_t _Np>
constexpr bool
__erased_less_than(const _Variant& __lhs, const _Variant& __rhs)
{
return __get<_Np>(std::forward<_Variant>(__lhs))
< __get<_Np>(std::forward<_Variant>(__rhs));
}
template<typename _Tp>
constexpr size_t
__erased_hash(void* __t)
{
return std::hash<remove_cv_t<remove_reference_t<_Tp>>>{}(
__ref_cast<_Tp>(__t));
}
// 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;
};
// Defines index and the dtor, possibly trivial.
template<bool __trivially_destructible, typename... _Types>
struct _Variant_storage;
template<typename... _Types>
struct _Variant_storage<false, _Types...>
{
template<size_t... __indices>
static constexpr void (*_S_vtable[])(const _Variant_storage&) =
{ &__erased_dtor<const _Variant_storage&, __indices>... };
constexpr _Variant_storage() : _M_index(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)
{ }
template<size_t... __indices>
constexpr void _M_reset_impl(std::index_sequence<__indices...>)
{
if (_M_index != variant_npos)
_S_vtable<__indices...>[_M_index](*this);
}
void _M_reset()
{
_M_reset_impl(std::index_sequence_for<_Types...>{});
_M_index = variant_npos;
}
~_Variant_storage()
{ _M_reset(); }
_Variadic_union<_Types...> _M_u;
size_t _M_index;
};
template<typename... _Types>
struct _Variant_storage<true, _Types...>
{
constexpr _Variant_storage() : _M_index(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()
{ _M_index = variant_npos; }
_Variadic_union<_Types...> _M_u;
size_t _M_index;
};
// Helps SFINAE on special member functions. Otherwise it can live in variant
// class.
template<typename... _Types>
struct _Variant_base :
_Variant_storage<(std::is_trivially_destructible_v<_Types> && ...),
_Types...>
{
using _Storage =
_Variant_storage<(std::is_trivially_destructible_v<_Types> && ...),
_Types...>;
constexpr
_Variant_base()
noexcept(is_nothrow_default_constructible_v<
variant_alternative_t<0, variant<_Types...>>>)
: _Variant_base(in_place_index<0>) { }
_Variant_base(const _Variant_base& __rhs)
{
if (__rhs._M_valid())
{
static constexpr void (*_S_vtable[])(void*, void*) =
{ &__erased_ctor<_Types&, const _Types&>... };
_S_vtable[__rhs._M_index](_M_storage(), __rhs._M_storage());
this->_M_index = __rhs._M_index;
}
}
_Variant_base(_Variant_base&& __rhs)
noexcept((is_nothrow_move_constructible_v<_Types> && ...))
{
if (__rhs._M_valid())
{
static constexpr void (*_S_vtable[])(void*, void*) =
{ &__erased_ctor<_Types&, _Types&&>... };
_S_vtable[__rhs._M_index](_M_storage(), __rhs._M_storage());
this->_M_index = __rhs._M_index;
}
}
template<size_t _Np, typename... _Args>
constexpr explicit
_Variant_base(in_place_index_t<_Np> __i, _Args&&... __args)
: _Storage(__i, std::forward<_Args>(__args)...)
{ }
_Variant_base&
operator=(const _Variant_base& __rhs)
{
if (this->_M_index == __rhs._M_index)
{
if (__rhs._M_valid())
{
static constexpr void (*_S_vtable[])(void*, void*) =
{ &__erased_assign<_Types&, const _Types&>... };
_S_vtable[__rhs._M_index](_M_storage(), __rhs._M_storage());
}
}
else
{
_Variant_base __tmp(__rhs);
this->~_Variant_base();
__try
{
::new (this) _Variant_base(std::move(__tmp));
}
__catch (...)
{
this->_M_index = variant_npos;
__throw_exception_again;
}
}
__glibcxx_assert(this->_M_index == __rhs._M_index);
return *this;
}
void _M_destructive_move(_Variant_base&& __rhs)
{
this->~_Variant_base();
__try
{
::new (this) _Variant_base(std::move(__rhs));
}
__catch (...)
{
this->_M_index = variant_npos;
__throw_exception_again;
}
}
_Variant_base&
operator=(_Variant_base&& __rhs)
noexcept((is_nothrow_move_constructible_v<_Types> && ...)
&& (is_nothrow_move_assignable_v<_Types> && ...))
{
if (this->_M_index == __rhs._M_index)
{
if (__rhs._M_valid())
{
static constexpr void (*_S_vtable[])(void*, void*) =
{ &__erased_assign<_Types&, _Types&&>... };
_S_vtable[__rhs._M_index](_M_storage(), __rhs._M_storage());
}
}
else
{
_M_destructive_move(std::move(__rhs));
}
return *this;
}
void*
_M_storage() const
{
return const_cast<void*>(static_cast<const void*>(
std::addressof(_Storage::_M_u)));
}
constexpr bool
_M_valid() const noexcept
{ return this->_M_index != variant_npos; }
};
// For how many times does _Tp appear in _Tuple?
template<typename _Tp, typename _Tuple>
struct __tuple_count;
template<typename _Tp, typename _Tuple>
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>
constexpr bool __exactly_once = __tuple_count_v<_Tp, tuple<_Types...>> == 1;
// Takes _Types and create an overloaded _S_fun for each type.
// If a type appears more than once in _Types, create only one overload.
template<typename... _Types>
struct __overload_set
{ static void _S_fun(); };
template<typename _First, typename... _Rest>
struct __overload_set<_First, _Rest...> : __overload_set<_Rest...>
{
using __overload_set<_Rest...>::_S_fun;
static integral_constant<size_t, sizeof...(_Rest)> _S_fun(_First);
};
template<typename... _Rest>
struct __overload_set<void, _Rest...> : __overload_set<_Rest...>
{
using __overload_set<_Rest...>::_S_fun;
};
// Helper for variant(_Tp&&) and variant::operator=(_Tp&&).
// __accepted_index maps the arbitrary _Tp to an alternative type in _Variant.
template<typename _Tp, typename _Variant, typename = void>
struct __accepted_index
{ static constexpr size_t value = variant_npos; };
template<typename _Tp, typename... _Types>
struct __accepted_index<
_Tp, variant<_Types...>,
decltype(__overload_set<_Types...>::_S_fun(std::declval<_Tp>()),
std::declval<void>())>
{
static constexpr size_t value = sizeof...(_Types) - 1
- decltype(__overload_set<_Types...>::
_S_fun(std::declval<_Tp>()))::value;
};
// Returns the raw storage for __v.
template<typename _Variant>
void* __get_storage(_Variant&& __v)
{ return __v._M_storage(); }
// Used for storing multi-dimensional vtable.
template<typename _Tp, size_t... _Dimensions>
struct _Multi_array
{
constexpr const _Tp&
_M_access() const
{ return _M_data; }
_Tp _M_data;
};
template<typename _Tp, size_t __first, size_t... __rest>
struct _Multi_array<_Tp, __first, __rest...>
{
template<typename... _Args>
constexpr const _Tp&
_M_access(size_t __first_index, _Args... __rest_indices) const
{ return _M_arr[__first_index]._M_access(__rest_indices...); }
_Multi_array<_Tp, __rest...> _M_arr[__first];
};
// 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 _Variant_tuple, typename _Index_seq>
struct __gen_vtable_impl;
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...>,
tuple<_Variants...>, 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...>)
{
(_S_apply_single_alt<__var_indices>(
__vtable._M_arr[__var_indices]), ...);
}
template<size_t __index, typename _Tp>
static constexpr void
_S_apply_single_alt(_Tp& __element)
{
using _Alternative = variant_alternative_t<__index, _Next>;
__element = __gen_vtable_impl<
remove_reference_t<
decltype(__element)>, tuple<_Variants...>,
std::index_sequence<__indices..., __index>>::_S_apply();
}
};
template<typename _Result_type, typename _Visitor, typename... _Variants,
size_t... __indices>
struct __gen_vtable_impl<
_Multi_array<_Result_type (*)(_Visitor, _Variants...)>,
tuple<_Variants...>, std::index_sequence<__indices...>>
{
using _Array_type =
_Multi_array<_Result_type (*)(_Visitor&&, _Variants...)>;
decltype(auto)
static constexpr __visit_invoke(_Visitor&& __visitor, _Variants... __vars)
{
return __invoke(std::forward<_Visitor>(__visitor),
std::get<__indices>(
std::forward<_Variants>(__vars))...);
}
static constexpr auto
_S_apply()
{ return _Array_type{&__visit_invoke}; }
};
template<typename _Result_type, typename _Visitor, typename... _Variants>
struct __gen_vtable
{
using _Func_ptr = _Result_type (*)(_Visitor&&, _Variants...);
using _Array_type =
_Multi_array<_Func_ptr,
variant_size_v<remove_reference_t<_Variants>>...>;
static constexpr _Array_type
_S_apply()
{
return __gen_vtable_impl<_Array_type, tuple<_Variants...>,
std::index_sequence<>>::_S_apply();
}
static constexpr auto _S_vtable = _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>>>... { };
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace __variant
} // namespace __detail
_GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Tp, typename... _Types>
inline constexpr bool holds_alternative(const variant<_Types...>& __v)
noexcept
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T should occur for exactly once in alternatives");
return __v.index() == __detail::__variant::__index_of_v<_Tp, _Types...>;
}
template<typename _Tp, typename... _Types>
constexpr inline _Tp& get(variant<_Types...>& __v)
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T should occur for exactly once in alternatives");
static_assert(!is_void_v<_Tp>, "_Tp should not be void");
return get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v);
}
template<typename _Tp, typename... _Types>
constexpr inline _Tp&& get(variant<_Types...>&& __v)
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T should occur for exactly once in alternatives");
static_assert(!is_void_v<_Tp>, "_Tp should not be void");
return get<__detail::__variant::__index_of_v<_Tp, _Types...>>(
std::move(__v));
}
template<typename _Tp, typename... _Types>
constexpr inline const _Tp& get(const variant<_Types...>& __v)
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T should occur for exactly once in alternatives");
static_assert(!is_void_v<_Tp>, "_Tp should not be void");
return get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v);
}
template<typename _Tp, typename... _Types>
constexpr inline const _Tp&& get(const variant<_Types...>&& __v)
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T should occur for exactly once in alternatives");
static_assert(!is_void_v<_Tp>, "_Tp should not be void");
return get<__detail::__variant::__index_of_v<_Tp, _Types...>>(
std::move(__v));
}
template<size_t _Np, typename... _Types>
constexpr inline
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 should be in [0, number of alternatives)");
static_assert(!is_void_v<_Alternative_type>, "_Tp should not be void");
if (__ptr && __ptr->index() == _Np)
return &__detail::__variant::__get<_Np>(*__ptr);
return nullptr;
}
template<size_t _Np, typename... _Types>
constexpr inline
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 should be in [0, number of alternatives)");
static_assert(!is_void_v<_Alternative_type>, "_Tp should not be void");
if (__ptr && __ptr->index() == _Np)
return &__detail::__variant::__get<_Np>(*__ptr);
return nullptr;
}
template<typename _Tp, typename... _Types>
constexpr inline add_pointer_t<_Tp>
get_if(variant<_Types...>* __ptr) noexcept
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T should occur for exactly once in alternatives");
static_assert(!is_void_v<_Tp>, "_Tp should not be void");
return get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>(__ptr);
}
template<typename _Tp, typename... _Types>
constexpr inline add_pointer_t<const _Tp>
get_if(const variant<_Types...>* __ptr)
noexcept
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T should occur for exactly once in alternatives");
static_assert(!is_void_v<_Tp>, "_Tp should not be void");
return get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>(__ptr);
}
template<typename... _Types>
constexpr bool operator==(const variant<_Types...>& __lhs,
const variant<_Types...>& __rhs)
{
return __lhs._M_equal_to(__rhs, std::index_sequence_for<_Types...>{});
}
template<typename... _Types>
constexpr inline bool
operator!=(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs)
{ return !(__lhs == __rhs); }
template<typename... _Types>
constexpr inline bool
operator<(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs)
{
return __lhs._M_less_than(__rhs, std::index_sequence_for<_Types...>{});
}
template<typename... _Types>
constexpr inline bool
operator>(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs)
{ return __rhs < __lhs; }
template<typename... _Types>
constexpr inline bool
operator<=(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs)
{ return !(__lhs > __rhs); }
template<typename... _Types>
constexpr inline bool
operator>=(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs)
{ return !(__lhs < __rhs); }
template<typename _Visitor, typename... _Variants>
constexpr decltype(auto) visit(_Visitor&&, _Variants&&...);
struct monostate { };
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; }
constexpr bool operator==(monostate, monostate) noexcept
{ return true; }
constexpr bool operator!=(monostate, monostate) noexcept
{ return false; }
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 : _M_reason("Unknown reason") { }
const char* what() const noexcept override
{ return _M_reason; }
private:
bad_variant_access(const char* __reason) : _M_reason(__reason) { }
const char* _M_reason;
friend void __throw_bad_variant_access(const char* __what);
};
inline void
__throw_bad_variant_access(const char* __what)
{ _GLIBCXX_THROW_OR_ABORT(bad_variant_access(__what)); }
template<typename... _Types>
class variant
: private __detail::__variant::_Variant_base<_Types...>,
private _Enable_default_constructor<
is_default_constructible_v<
variant_alternative_t<0, variant<_Types...>>>, variant<_Types...>>,
private _Enable_copy_move<
(is_copy_constructible_v<_Types> && ...),
(is_copy_constructible_v<_Types> && ...)
&& (is_move_constructible_v<_Types> && ...)
&& (is_copy_assignable_v<_Types> && ...),
(is_move_constructible_v<_Types> && ...),
(is_move_constructible_v<_Types> && ...)
&& (is_move_assignable_v<_Types> && ...),
variant<_Types...>>
{
private:
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<
is_default_constructible_v<
variant_alternative_t<0, variant<_Types...>>>, variant<_Types...>>;
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, bool = _Np < sizeof...(_Types)>
struct __to_type_impl;
template<size_t _Np>
struct __to_type_impl<_Np, true>
{ using type = variant_alternative_t<_Np, variant>; };
template<size_t _Np>
using __to_type = typename __to_type_impl<_Np>::type;
template<typename _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...>;
public:
constexpr variant()
noexcept(is_nothrow_default_constructible_v<__to_type<0>>) = default;
variant(const variant&) = default;
variant(variant&&)
noexcept((is_nothrow_move_constructible_v<_Types> && ...)) = default;
template<typename _Tp,
typename = enable_if_t<__exactly_once<__accepted_type<_Tp&&>>
&& is_constructible_v<__accepted_type<_Tp&&>, _Tp&&>
&& !is_same_v<decay_t<_Tp>, variant>>>
constexpr
variant(_Tp&& __t)
noexcept(is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp&&>)
: variant(in_place_index<__accepted_index<_Tp&&>>, std::forward<_Tp>(__t))
{ __glibcxx_assert(holds_alternative<__accepted_type<_Tp&&>>(*this)); }
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)...)
{ __glibcxx_assert(holds_alternative<_Tp>(*this)); }
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)...)
{ __glibcxx_assert(holds_alternative<_Tp>(*this)); }
template<size_t _Np, typename... _Args,
typename = enable_if_t<
is_constructible_v<__to_type<_Np>, _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{})
{ __glibcxx_assert(index() == _Np); }
template<size_t _Np, typename _Up, typename... _Args,
typename = enable_if_t<is_constructible_v<__to_type<_Np>,
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{})
{ __glibcxx_assert(index() == _Np); }
~variant() = default;
variant& operator=(const variant&) = default;
variant& operator=(variant&&)
noexcept((is_nothrow_move_constructible_v<_Types> && ...)
&& (is_nothrow_move_assignable_v<_Types> && ...)) = default;
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&&>
&& !is_same_v<decay_t<_Tp>, variant>, 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
this->emplace<__index>(std::forward<_Tp>(__rhs));
__glibcxx_assert(holds_alternative<__accepted_type<_Tp&&>>(*this));
return *this;
}
template<typename _Tp, typename... _Args>
enable_if_t<is_constructible_v<_Tp, _Args...> && __exactly_once<_Tp>>
emplace(_Args&&... __args)
{
this->emplace<__index_of<_Tp>>(std::forward<_Args>(__args)...);
__glibcxx_assert(holds_alternative<_Tp>(*this));
}
template<typename _Tp, typename _Up, typename... _Args>
enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>
&& __exactly_once<_Tp>>
emplace(initializer_list<_Up> __il, _Args&&... __args)
{
this->emplace<__index_of<_Tp>>(__il, std::forward<_Args>(__args)...);
__glibcxx_assert(holds_alternative<_Tp>(*this));
}
template<size_t _Np, typename... _Args>
enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>,
_Args...>>
emplace(_Args&&... __args)
{
static_assert(_Np < sizeof...(_Types),
"The index should be in [0, number of alternatives)");
this->~variant();
__try
{
::new (this) variant(in_place_index<_Np>,
std::forward<_Args>(__args)...);
}
__catch (...)
{
this->_M_index = variant_npos;
__throw_exception_again;
}
__glibcxx_assert(index() == _Np);
}
template<size_t _Np, typename _Up, typename... _Args>
enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>,
initializer_list<_Up>&, _Args...>>
emplace(initializer_list<_Up> __il, _Args&&... __args)
{
static_assert(_Np < sizeof...(_Types),
"The index should be in [0, number of alternatives)");
this->~variant();
__try
{
::new (this) variant(in_place_index<_Np>, __il,
std::forward<_Args>(__args)...);
}
__catch (...)
{
this->_M_index = variant_npos;
__throw_exception_again;
}
__glibcxx_assert(index() == _Np);
}
constexpr bool valueless_by_exception() const noexcept
{ return !this->_M_valid(); }
constexpr size_t index() const noexcept
{ return this->_M_index; }
void
swap(variant& __rhs)
noexcept((__is_nothrow_swappable<_Types>::value && ...)
&& is_nothrow_move_constructible_v<variant>)
{
if (this->index() == __rhs.index())
{
if (this->_M_valid())
{
static constexpr void (*_S_vtable[])(void*, void*) =
{ &__detail::__variant::__erased_swap<_Types&, _Types&>... };
_S_vtable[__rhs._M_index](this->_M_storage(),
__rhs._M_storage());
}
}
else if (!this->_M_valid())
{
this->_M_destructive_move(std::move(__rhs));
__rhs._M_reset();
}
else if (!__rhs._M_valid())
{
__rhs._M_destructive_move(std::move(*this));
this->_M_reset();
}
else
{
auto __tmp = std::move(__rhs);
__rhs._M_destructive_move(std::move(*this));
this->_M_destructive_move(std::move(__tmp));
}
}
private:
template<size_t... __indices>
static constexpr bool
(*_S_equal_to_vtable[])(const variant&, const variant&) =
{ &__detail::__variant::__erased_equal_to<
const variant&, __indices>... };
template<size_t... __indices>
static constexpr bool
(*_S_less_than_vtable[])(const variant&, const variant&) =
{ &__detail::__variant::__erased_less_than<
const variant&, __indices>... };
template<size_t... __indices>
constexpr bool
_M_equal_to(const variant& __rhs,
std::index_sequence<__indices...>) const
{
if (this->index() != __rhs.index())
return false;
if (this->valueless_by_exception())
return true;
return _S_equal_to_vtable<__indices...>[this->index()](*this, __rhs);
}
template<size_t... __indices>
constexpr inline bool
_M_less_than(const variant& __rhs,
std::index_sequence<__indices...>) const
{
auto __lhs_index = this->index();
auto __rhs_index = __rhs.index();
if (__lhs_index < __rhs_index)
return true;
if (__lhs_index > __rhs_index)
return false;
if (this->valueless_by_exception())
return false;
return _S_less_than_vtable<__indices...>[__lhs_index](*this, __rhs);
}
template<size_t _Np, typename _Vp>
friend constexpr decltype(auto) __detail::__variant::
#if _GLIBCXX_INLINE_VERSION
__7:: // Required due to PR c++/59256
#endif
__get(_Vp&& __v);
template<typename _Vp>
friend void* __detail::__variant::
#if _GLIBCXX_INLINE_VERSION
__7:: // Required due to PR c++/59256
#endif
__get_storage(_Vp&& __v);
template<typename... _Tp>
friend constexpr bool
operator==(const variant<_Tp...>& __lhs,
const variant<_Tp...>& __rhs);
template<typename... _Tp>
friend constexpr bool
operator<(const variant<_Tp...>& __lhs,
const variant<_Tp...>& __rhs);
};
template<size_t _Np, typename... _Types>
constexpr variant_alternative_t<_Np, variant<_Types...>>&
get(variant<_Types...>& __v)
{
static_assert(_Np < sizeof...(_Types),
"The index should be in [0, number of alternatives)");
if (__v.index() != _Np)
__throw_bad_variant_access("Unexpected index");
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 should be in [0, number of alternatives)");
if (__v.index() != _Np)
__throw_bad_variant_access("Unexpected index");
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 should be in [0, number of alternatives)");
if (__v.index() != _Np)
__throw_bad_variant_access("Unexpected index");
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 should be in [0, number of alternatives)");
if (__v.index() != _Np)
__throw_bad_variant_access("Unexpected index");
return __detail::__variant::__get<_Np>(std::move(__v));
}
template<typename _Visitor, typename... _Variants>
constexpr decltype(auto)
visit(_Visitor&& __visitor, _Variants&&... __variants)
{
if ((__variants.valueless_by_exception() || ...))
__throw_bad_variant_access("Unexpected index");
using _Result_type =
decltype(std::forward<_Visitor>(__visitor)(get<0>(__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)...);
}
template<typename... _Types>
struct hash<variant<_Types...>>
: private __detail::__variant::_Variant_hash_base<
variant<_Types...>, std::index_sequence_for<_Types...>>
{
using result_type = size_t;
using argument_type = variant<_Types...>;
size_t
operator()(const variant<_Types...>& __t) const
noexcept((is_nothrow_callable_v<hash<decay_t<_Types>>(_Types)> && ...))
{
if (!__t.valueless_by_exception())
{
namespace __edv = __detail::__variant;
static constexpr size_t (*_S_vtable[])(void*) =
{ &__edv::__erased_hash<const _Types&>... };
return hash<size_t>{}(__t.index())
+ _S_vtable[__t.index()](__edv::__get_storage(__t));
}
return hash<size_t>{}(__t.index());
}
};
template<>
struct hash<monostate>
{
using result_type = size_t;
using argument_type = monostate;
size_t
operator()(const monostate& __t) const noexcept
{
constexpr size_t __magic_monostate_hash = -7777;
return __magic_monostate_hash;
}
};
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif // C++17
#endif // _GLIBCXX_VARIANT
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