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c42bc5d73b
gcc/libstdc++-v3/include/std/variant
Tim Shen c42bc5d73b variant (variant::operator=): Fix assignment on references. 
* libstdc++-v3/include/std/variant (variant::operator=): Fix assignment
	on references.
	* libstdc++-v3/testsuite/20_util/variant/compile.cc: Add test.

From-SVN: r240343
2016-09-22 08:45:55 +00:00

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// <variant> -*- C++ -*-
// Copyright (C) 2016 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/move.h>
#include <bits/uses_allocator.h>
namespace std _GLIBCXX_VISIBILITY(default)
{
_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;
constexpr size_t variant_npos = -1;
namespace __detail
{
namespace __variant
{
// 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> {};
// Extract _From's qualifiers and references and apply it to _To.
// __reserved_type_map<const int&, char> is const char&.
template<typename _From, typename _To>
struct __reserved_type_map_impl
{ using type = _To; };
template<typename _From, typename _To>
using __reserved_type_map =
typename __reserved_type_map_impl<_From, _To>::type;
template<typename _From, typename _To>
struct __reserved_type_map_impl<_From&, _To>
{ using type = add_lvalue_reference_t<__reserved_type_map<_From, _To>>; };
template<typename _From, typename _To>
struct __reserved_type_map_impl<_From&&, _To>
{ using type = add_rvalue_reference_t<__reserved_type_map<_From, _To>>; };
template<typename _From, typename _To>
struct __reserved_type_map_impl<const _From, _To>
{ using type = add_const_t<__reserved_type_map<_From, _To>>; };
template<typename _From, typename _To>
struct __reserved_type_map_impl<volatile _From, _To>
{ using type = add_volatile_t<__reserved_type_map<_From, _To>>; };
template<typename _From, typename _To>
struct __reserved_type_map_impl<const volatile _From, _To>
{ using type = add_cv_t<__reserved_type_map<_From, _To>>; };
// Stores a reference alternative as a... well, reference.
template<typename _Reference>
struct _Reference_storage
{
static_assert(is_reference_v<_Reference>,
"BUG: _Reference should be a reference");
_Reference_storage(_Reference __ref) noexcept : _M_storage(__ref) { }
operator _Reference() noexcept
{ return static_cast<_Reference>(_M_storage); }
_Reference _M_storage;
};
// Stores a void alternative, because it is not a regular type.
template<typename _Void>
struct _Void_storage { };
// Map from the alternative type to a non-qualified storage type.
template<typename _Alternative, typename = void>
struct __storage_type
{ using type = _Alternative; };
template<typename _Alternative>
struct __storage_type<_Alternative,
enable_if_t<is_reference_v<_Alternative>>>
{ using type = _Reference_storage<_Alternative>; };
template<typename _Alternative>
struct __storage_type<_Alternative, enable_if_t<is_void_v<_Alternative>>>
{ using type = _Void_storage<_Alternative>; };
template<typename _Type>
using __storage = typename __storage_type<_Type>::type;
template<typename _Type, bool __is_literal = std::is_literal_type_v<_Type>>
struct _Uninitialized;
template<typename _Type>
struct _Uninitialized<_Type, true>
{
constexpr _Uninitialized() = default;
template<typename... _Args>
constexpr _Uninitialized(in_place_index_t<0>, _Args&&... __args)
: _M_storage(std::forward<_Args>(__args)...)
{ }
_Type _M_storage;
};
template<typename _Type>
struct _Uninitialized<_Type, false>
{
constexpr _Uninitialized() = default;
template<typename... _Args>
constexpr _Uninitialized(in_place_index_t<0>, _Args&&... __args)
{ ::new (&_M_storage) _Type(std::forward<_Args>(__args)...); }
typename std::aligned_storage<sizeof(_Type), alignof(_Type)>::type
_M_storage;
};
// Reverse mapping of __storage_type.
template<typename _Storage_type>
struct __alternative_type
{
static_assert(!is_reference_v<_Storage_type>,
"BUG: _Storage_type should not be reference");
using type = _Storage_type;
};
template<typename _Reference>
struct __alternative_type<_Reference_storage<_Reference>>
{ using type = _Reference; };
template<typename _Void>
struct __alternative_type<_Void_storage<_Void>>
{ using type = _Void; };
// Given a qualified storage type, return the desired reference.
// The qualified storage type is supposed to carry the variant object's
// qualifications and reference information, and the designated alternative's
// storage type.
// Returns the qualification-collapsed alternative references.
//
// For example, __get_alternative<_Reference_storage<int&&>&> returns int&.
template<typename _Qualified_storage>
decltype(auto)
__get_alternative(void* __ptr)
{
using _Storage = decay_t<_Qualified_storage>;
using _Alternative = typename __alternative_type<_Storage>::type;
return __reserved_type_map<_Qualified_storage, _Alternative>(
*static_cast<_Storage*>(__ptr));
}
// 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) decay_t<_Lhs>(__get_alternative<_Rhs>(__rhs)); }
template<typename _Alloc, typename _Lhs, typename _Rhs>
constexpr void
__erased_use_alloc_ctor(const _Alloc& __a, void* __lhs, void* __rhs)
{
__uses_allocator_construct(__a, static_cast<decay_t<_Lhs>*>(__lhs),
__get_alternative<_Rhs>(__rhs));
}
// TODO: Find a potential chance to reuse this accross the project.
template<typename _Tp>
constexpr void
__erased_dtor(void* __ptr)
{
using _Storage = decay_t<_Tp>;
static_cast<_Storage*>(__ptr)->~_Storage();
}
template<typename _Lhs, typename _Rhs>
constexpr void
__erased_assign(void* __lhs, void* __rhs)
{ __get_alternative<_Lhs>(__lhs) = __get_alternative<_Rhs>(__rhs); }
template<typename _Lhs, typename _Rhs>
constexpr void
__erased_swap(void* __lhs, void* __rhs)
{
using std::swap;
swap(__get_alternative<_Lhs>(__lhs), __get_alternative<_Rhs>(__rhs));
}
template<typename _Lhs, typename _Rhs>
constexpr bool
__erased_equal_to(void* __lhs, void* __rhs)
{ return __get_alternative<_Lhs>(__lhs) == __get_alternative<_Rhs>(__rhs); }
template<typename _Lhs, typename _Rhs>
constexpr bool
__erased_less_than(void* __lhs, void* __rhs)
{ return __get_alternative<_Lhs>(__lhs) < __get_alternative<_Rhs>(__rhs); }
template<typename _Tp>
constexpr size_t
__erased_hash(void* __t)
{ return std::hash<decay_t<_Tp>>{}(__get_alternative<_Tp>(__t)); }
template<typename... _Types>
struct _Variant_base;
template<typename... _Types>
struct _Variant_storage
{ constexpr _Variant_storage() = default; };
// Use recursive unions to implement a trivially destructible variant.
template<typename _First, typename... _Rest>
struct _Variant_storage<_First, _Rest...>
{
constexpr _Variant_storage() = default;
template<size_t _Np, typename... _Args>
constexpr _Variant_storage(in_place_index_t<_Np>, _Args&&... __args)
: _M_union(in_place<_Np>, forward<_Args>(__args)...)
{ }
~_Variant_storage() = default;
constexpr void*
_M_storage() const
{
return const_cast<void*>(
static_cast<const void*>(std::addressof(_M_union._M_first._M_storage)));
}
union _Union
{
constexpr _Union() {};
template<typename... _Args>
constexpr _Union(in_place_index_t<0>, _Args&&... __args)
: _M_first(in_place<0>, forward<_Args>(__args)...)
{ }
template<size_t _Np, typename... _Args,
typename = enable_if_t<0 < _Np && _Np < sizeof...(_Rest) + 1>>
constexpr _Union(in_place_index_t<_Np>, _Args&&... __args)
: _M_rest(in_place<_Np - 1>, forward<_Args>(__args)...)
{ }
_Uninitialized<__storage<_First>> _M_first;
_Variant_storage<_Rest...> _M_rest;
} _M_union;
};
template<typename _Derived, bool __is_trivially_destructible>
struct _Dtor_mixin
{
~_Dtor_mixin()
{ static_cast<_Derived*>(this)->_M_destroy(); }
};
template<typename _Derived>
struct _Dtor_mixin<_Derived, true>
{
~_Dtor_mixin() = default;
};
// Helps SFINAE on special member functions. Otherwise it can live in variant
// class.
template<typename... _Types>
struct _Variant_base :
_Variant_storage<_Types...>,
_Dtor_mixin<_Variant_base<_Types...>,
__and_<std::is_trivially_destructible<_Types>...>::value>
{
using _Storage = _Variant_storage<_Types...>;
constexpr
_Variant_base()
noexcept(is_nothrow_default_constructible_v<
variant_alternative_t<0, variant<_Types...>>>)
: _Variant_base(in_place<0>) { }
_Variant_base(const _Variant_base& __rhs)
: _Storage(), _M_index(__rhs._M_index)
{
if (__rhs._M_valid())
{
static constexpr void (*_S_vtable[])(void*, void*) =
{ &__erased_ctor<__storage<_Types>&,
const __storage<_Types>&>... };
_S_vtable[__rhs._M_index](_M_storage(), __rhs._M_storage());
}
}
_Variant_base(_Variant_base&& __rhs)
noexcept(__and_<is_nothrow_move_constructible<_Types>...>::value)
: _Storage(), _M_index(__rhs._M_index)
{
if (__rhs._M_valid())
{
static constexpr void (*_S_vtable[])(void*, void*) =
{ &__erased_ctor<__storage<_Types>&, __storage<_Types>&&>... };
_S_vtable[__rhs._M_index](_M_storage(), __rhs._M_storage());
}
}
template<size_t _Np, typename... _Args>
constexpr explicit
_Variant_base(in_place_index_t<_Np> __i, _Args&&... __args)
: _Storage(__i, forward<_Args>(__args)...), _M_index(_Np)
{ }
template<typename _Alloc>
_Variant_base(const _Alloc& __a, const _Variant_base& __rhs)
: _Storage(), _M_index(__rhs._M_index)
{
if (__rhs._M_valid())
{
static constexpr void
(*_S_vtable[])(const _Alloc&, void*, void*) =
{ &__erased_use_alloc_ctor<_Alloc, __storage<_Types>&,
const __storage<_Types>&>... };
_S_vtable[__rhs._M_index](__a, _M_storage(), __rhs._M_storage());
}
}
template<typename _Alloc>
_Variant_base(const _Alloc& __a, _Variant_base&& __rhs)
: _Storage(), _M_index(__rhs._M_index)
{
if (__rhs._M_valid())
{
static constexpr void
(*_S_vtable[])(const _Alloc&, void*, void*) =
{ &__erased_use_alloc_ctor<_Alloc, __storage<_Types>&,
__storage<_Types>&&>... };
_S_vtable[__rhs._M_index](__a, _M_storage(), __rhs._M_storage());
}
}
template<typename _Alloc, size_t _Np, typename... _Args>
constexpr explicit
_Variant_base(const _Alloc& __a, in_place_index_t<_Np>,
_Args&&... __args)
: _Storage(), _M_index(_Np)
{
using _Storage =
__storage<variant_alternative_t<_Np, variant<_Types...>>>;
__uses_allocator_construct(__a, static_cast<_Storage*>(_M_storage()),
forward<_Args>(__args)...);
__glibcxx_assert(_M_index == _Np);
}
_Variant_base&
operator=(const _Variant_base& __rhs)
{
if (_M_index == __rhs._M_index)
{
if (__rhs._M_valid())
{
static constexpr void (*_S_vtable[])(void*, void*) =
{ &__erased_assign<__storage<_Types>&,
const __storage<_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 (...)
{
_M_index = variant_npos;
__throw_exception_again;
}
}
__glibcxx_assert(_M_index == __rhs._M_index);
return *this;
}
_Variant_base&
operator=(_Variant_base&& __rhs)
noexcept(__and_<is_nothrow_move_constructible<_Types>...,
is_nothrow_move_assignable<_Types>...>::value)
{
if (_M_index == __rhs._M_index)
{
if (__rhs._M_valid())
{
static constexpr void (*_S_vtable[])(void*, void*) =
{ &__erased_assign<__storage<_Types>&,
__storage<_Types>&&>... };
_S_vtable[__rhs._M_index](_M_storage(), __rhs._M_storage());
}
}
else
{
this->~_Variant_base();
__try
{
::new (this) _Variant_base(std::move(__rhs));
}
__catch (...)
{
_M_index = variant_npos;
__throw_exception_again;
}
}
return *this;
}
void _M_destroy()
{
if (_M_valid())
{
static constexpr void (*_S_vtable[])(void*) =
{ &__erased_dtor<__storage<_Types>&>... };
_S_vtable[this->_M_index](_M_storage());
}
}
constexpr void*
_M_storage() const
{ return _Storage::_M_storage(); }
constexpr bool
_M_valid() const noexcept
{ return _M_index != variant_npos; }
size_t _M_index;
};
// 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(); }
// Returns the reference to the desired alternative.
// It is as unsafe as a reinterpret_cast.
template<typename _Tp, typename _Variant>
decltype(auto) __access(_Variant&& __v)
{
return __get_alternative<__reserved_type_map<_Variant&&, __storage<_Tp>>>(
__get_storage(forward<_Variant>(__v)));
}
// A helper used to create variadic number of _To types.
template<typename _From, typename _To>
using _To_type = _To;
// Call the actual visitor.
// _Args are qualified storage types.
template<typename _Visitor, typename... _Args>
decltype(auto) __visit_invoke(_Visitor&& __visitor,
_To_type<_Args, void*>... __ptrs)
{
return forward<_Visitor>(__visitor)(__get_alternative<_Args>(__ptrs)...);
}
// 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.
// _Variant_tuple is initially the input from visit(), and gets gradually
// consumed.
// _Arg_tuple is enumerated alternative sequence, represented by a
// qualified storage.
//
// For example,
// visit([](auto, auto){},
// variant<int, char>(),
// variant<float, double, long double>())
// will trigger instantiations of:
// __gen_vtable_impl<_Multi_array<void(*)(void*, void*), 2, 3>,
// tuple<variant<int, char>,
// variant<float, double, long double>>,
// tuple<>>
// __gen_vtable_impl<_Multi_array<void(*)(void*, void*), 3>,
// tuple<variant<float, double, long double>>,
// tuple<int>>
// __gen_vtable_impl<_Multi_array<void(*)(void*, void*)>,
// tuple<>,
// tuple<int, float>>
// __gen_vtable_impl<_Multi_array<void(*)(void*, void*)>,
// tuple<>,
// tuple<int, double>>
// __gen_vtable_impl<_Multi_array<void(*)(void*, void*)>,
// tuple<>,
// tuple<int, long double>>
// __gen_vtable_impl<_Multi_array<void(*)(void*, void*), 3>,
// tuple<variant<float, double, long double>>,
// tuple<char>>
// __gen_vtable_impl<_Multi_array<void(*)(void*, void*)>,
// tuple<>,
// tuple<char, float>>
// __gen_vtable_impl<_Multi_array<void(*)(void*, void*)>,
// tuple<>,
// tuple<char, double>>
// __gen_vtable_impl<_Multi_array<void(*)(void*, void*)>,
// tuple<>,
// tuple<char, long double>>
// The returned multi-dimensional vtable can be fast accessed by the visitor
// using index calculation.
template<typename _Array_type, typename _Variant_tuple, typename _Arg_tuple>
struct __gen_vtable_impl;
template<typename _Array_type, typename _First, typename... _Rest,
typename... _Args>
struct __gen_vtable_impl<_Array_type, tuple<_First, _Rest...>,
tuple<_Args...>>
{
static constexpr _Array_type
_S_apply()
{
_Array_type __vtable{};
_S_apply_all_alts(
__vtable, make_index_sequence<variant_size_v<decay_t<_First>>>());
return __vtable;
}
template<size_t... __indices>
static constexpr void
_S_apply_all_alts(_Array_type& __vtable, index_sequence<__indices...>)
{ (_S_apply_single_alt<__indices>(__vtable._M_arr[__indices]), ...); }
template<size_t __index>
static constexpr void
_S_apply_single_alt(auto& __element)
{
using _Alternative = variant_alternative_t<__index, decay_t<_First>>;
using _Qualified_storage = __reserved_type_map<
_First, __storage<_Alternative>>;
__element = __gen_vtable_impl<
decay_t<decltype(__element)>, tuple<_Rest...>,
tuple<_Args..., _Qualified_storage>>::_S_apply();
}
};
template<typename _Result_type, typename _Visitor, typename... _Args>
struct __gen_vtable_impl<
_Multi_array<_Result_type (*)(_Visitor, _To_type<_Args, void*>...)>,
tuple<>, tuple<_Args...>>
{
using _Array_type =
_Multi_array<_Result_type (*)(_Visitor&&, _To_type<_Args, void*>...)>;
static constexpr auto
_S_apply()
{ return _Array_type{&__visit_invoke<_Visitor, _Args...>}; }
};
template<typename _Result_type, typename _Visitor, typename... _Variants>
struct __gen_vtable
{
using _Func_ptr =
_Result_type (*)(_Visitor&&, _To_type<_Variants, void*>...);
using _Array_type =
_Multi_array<_Func_ptr, variant_size_v<decay_t<_Variants>>...>;
static constexpr _Array_type
_S_apply()
{
return __gen_vtable_impl<
_Array_type, tuple<_Variants...>, tuple<>>::_S_apply();
}
};
} // namespace __variant
} // namespace __detail
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<size_t _Np, typename... _Types>
variant_alternative_t<_Np, variant<_Types...>>&
get(variant<_Types...>&);
template<size_t _Np, typename... _Types>
variant_alternative_t<_Np, variant<_Types...>>&&
get(variant<_Types...>&&);
template<size_t _Np, typename... _Types>
variant_alternative_t<_Np, variant<_Types...>> const&
get(const variant<_Types...>&);
template<size_t _Np, typename... _Types>
variant_alternative_t<_Np, variant<_Types...>> const&&
get(const variant<_Types...>&&);
template<typename _Tp, typename... _Types>
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>
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>
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>
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>
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::__access<_Alternative_type>(*__ptr);
return nullptr;
}
template<size_t _Np, typename... _Types>
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::__access<_Alternative_type>(*__ptr);
return nullptr;
}
template<typename _Tp, typename... _Types>
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>
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>
bool operator==(const variant<_Types...>& __lhs,
const variant<_Types...>& __rhs)
{
if (__lhs.index() != __rhs.index())
return false;
if (__lhs.valueless_by_exception())
return true;
using __detail::__variant::__storage;
static constexpr bool (*_S_vtable[])(void*, void*) =
{ &__detail::__variant::__erased_equal_to<
const __storage<_Types>&, const __storage<_Types>&>... };
return _S_vtable[__lhs.index()](
__detail::__variant::__get_storage(__lhs),
__detail::__variant::__get_storage(__rhs));
}
template<typename... _Types>
inline bool
operator!=(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs)
{ return !(__lhs == __rhs); }
template<typename... _Types>
inline bool
operator<(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs)
{
if (__lhs.index() < __rhs.index())
return true;
if (__lhs.index() > __rhs.index())
return false;
if (__lhs.valueless_by_exception())
return false;
using __detail::__variant::__storage;
static constexpr bool (*_S_vtable[])(void*, void*) =
{ &__detail::__variant::__erased_less_than<
const __storage<_Types>&,
const __storage<_Types>&>... };
return _S_vtable[__lhs.index()](
__detail::__variant::__get_storage(__lhs),
__detail::__variant::__get_storage(__rhs));
}
template<typename... _Types>
inline bool
operator>(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs)
{ return __rhs < __lhs; }
template<typename... _Types>
inline bool
operator<=(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs)
{ return !(__lhs > __rhs); }
template<typename... _Types>
inline bool
operator>=(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs)
{ return !(__lhs < __rhs); }
template<typename _Visitor, typename... _Variants>
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 auto swap(variant<_Types...>& __lhs, variant<_Types...>& __rhs)
noexcept(noexcept(__lhs.swap(__rhs))) -> decltype(__lhs.swap(__rhs))
{ __lhs.swap(__rhs); }
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<
__and_<is_copy_constructible<_Types>...>::value,
__and_<is_copy_constructible<_Types>...,
is_move_constructible<_Types>...,
is_copy_assignable<_Types>...>::value,
__and_<is_move_constructible<_Types>...>::value,
__and_<is_move_constructible<_Types>...,
is_move_assignable<_Types>...>::value,
variant<_Types...>>
{
private:
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>
using __storage = __detail::__variant::__storage<_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(__and_<
is_nothrow_move_constructible<_Types>...>::value) = 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<__accepted_index<_Tp&&>>, 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_of<_Tp>>, 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_of<_Tp>>, __il,
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<_Np>, 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<_Np>, __il, forward<_Args>(__args)...),
_Default_ctor_enabler(_Enable_default_constructor_tag{})
{ __glibcxx_assert(index() == _Np); }
template<typename _Alloc,
typename = enable_if_t<
__is_uses_allocator_constructible_v<__to_type<0>, _Alloc>>>
variant(allocator_arg_t, const _Alloc& __a)
: variant(allocator_arg, __a, in_place<0>)
{ }
template<typename _Alloc,
typename = enable_if_t<__and_<__is_uses_allocator_constructible<
_Types, _Alloc,
add_lvalue_reference_t<add_const_t<_Types>>>...>::value>>
variant(allocator_arg_t, const _Alloc& __a, const variant& __rhs)
: _Base(__a, __rhs),
_Default_ctor_enabler(_Enable_default_constructor_tag{})
{ }
template<typename _Alloc,
typename = enable_if_t<__and_<
__is_uses_allocator_constructible<
_Types, _Alloc, add_rvalue_reference_t<_Types>>...>::value>>
variant(allocator_arg_t, const _Alloc& __a, variant&& __rhs)
: _Base(__a, std::move(__rhs)),
_Default_ctor_enabler(_Enable_default_constructor_tag{})
{ }
template<typename _Alloc, typename _Tp,
typename = enable_if_t<
__exactly_once<__accepted_type<_Tp&&>>
&& __is_uses_allocator_constructible_v<
__accepted_type<_Tp&&>, _Alloc, _Tp&&>
&& !is_same_v<decay_t<_Tp>, variant>, variant&>>
variant(allocator_arg_t, const _Alloc& __a, _Tp&& __t)
: variant(allocator_arg, __a, in_place<__accepted_index<_Tp&&>>,
forward<_Tp>(__t))
{ __glibcxx_assert(holds_alternative<__accepted_type<_Tp&&>>(*this)); }
template<typename _Alloc, typename _Tp, typename... _Args,
typename = enable_if_t<
__exactly_once<_Tp>
&& __is_uses_allocator_constructible_v<
_Tp, _Alloc, _Args&&...>>>
variant(allocator_arg_t, const _Alloc& __a, in_place_type_t<_Tp>,
_Args&&... __args)
: variant(allocator_arg, __a, in_place<__index_of<_Tp>>,
forward<_Args>(__args)...)
{ __glibcxx_assert(holds_alternative<_Tp>(*this)); }
template<typename _Alloc, typename _Tp, typename _Up, typename... _Args,
typename = enable_if_t<
__exactly_once<_Tp>
&& __is_uses_allocator_constructible_v<
_Tp, _Alloc, initializer_list<_Up>&, _Args&&...>>>
variant(allocator_arg_t, const _Alloc& __a, in_place_type_t<_Tp>,
initializer_list<_Up> __il, _Args&&... __args)
: variant(allocator_arg, __a, in_place<__index_of<_Tp>>, __il,
forward<_Args>(__args)...)
{ __glibcxx_assert(holds_alternative<_Tp>(*this)); }
template<typename _Alloc, size_t _Np, typename... _Args,
typename = enable_if_t<
__is_uses_allocator_constructible_v<
__to_type<_Np>, _Alloc, _Args&&...>>>
variant(allocator_arg_t, const _Alloc& __a, in_place_index_t<_Np>,
_Args&&... __args)
: _Base(__a, in_place<_Np>, forward<_Args>(__args)...),
_Default_ctor_enabler(_Enable_default_constructor_tag{})
{ __glibcxx_assert(index() == _Np); }
template<typename _Alloc, size_t _Np, typename _Up, typename... _Args,
typename = enable_if_t<
__is_uses_allocator_constructible_v<
__to_type<_Np>, _Alloc, initializer_list<_Up>&, _Args&&...>>>
variant(allocator_arg_t, const _Alloc& __a, in_place_index_t<_Np>,
initializer_list<_Up> __il, _Args&&... __args)
: _Base(__a, in_place<_Np>, __il, 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(__and_<is_nothrow_move_constructible<_Types>...,
is_nothrow_move_assignable<_Types>...>::value) = 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>(forward<_Tp>(__rhs));
__glibcxx_assert(holds_alternative<__accepted_type<_Tp&&>>(*this));
return *this;
}
template<typename _Tp, typename... _Args>
void emplace(_Args&&... __args)
{
static_assert(__exactly_once<_Tp>,
"T should occur for exactly once in alternatives");
this->emplace<__index_of<_Tp>>(forward<_Args>(__args)...);
__glibcxx_assert(holds_alternative<_Tp>(*this));
}
template<typename _Tp, typename _Up, typename... _Args>
void emplace(initializer_list<_Up> __il, _Args&&... __args)
{
static_assert(__exactly_once<_Tp>,
"T should occur for exactly once in alternatives");
this->emplace<__index_of<_Tp>>(__il, forward<_Args>(__args)...);
__glibcxx_assert(holds_alternative<_Tp>(*this));
}
template<size_t _Np, typename... _Args>
void 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<_Np>,
forward<_Args>(__args)...);
}
__catch (...)
{
this->_M_index = variant_npos;
__throw_exception_again;
}
__glibcxx_assert(index() == _Np);
}
template<size_t _Np, typename _Up, typename... _Args>
void 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<_Np>, __il,
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(__and_<__is_nothrow_swappable<_Types>...>::value
&& is_nothrow_move_assignable_v<variant>)
{
if (this->index() == __rhs.index())
{
if (this->_M_valid())
{
static constexpr void (*_S_vtable[])(void*, void*) =
{ &__detail::__variant::__erased_swap<
__storage<_Types>&, __storage<_Types>&>... };
_S_vtable[__rhs._M_index](this->_M_storage(),
__rhs._M_storage());
}
}
else if (!this->_M_valid())
{
*this = std::move(__rhs);
}
else if (!__rhs._M_valid())
{
__rhs = std::move(*this);
}
else
{
auto __tmp = std::move(__rhs);
__rhs = std::move(*this);
*this = std::move(__tmp);
}
}
template<typename _Vp>
friend void* __detail::__variant::__get_storage(_Vp&& __v);
};
// To honor algebraic data type, variant<> should be a bottom type, which
// is 0 (as opposed to a void type, which is 1). Use incomplete type to model
// bottom type.
template<> class variant<>;
template<size_t _Np, typename... _Types>
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::__access<
variant_alternative_t<_Np, variant<_Types...>>>(__v);
}
template<size_t _Np, typename... _Types>
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::__access<
variant_alternative_t<_Np, variant<_Types...>>>(std::move(__v));
}
template<size_t _Np, typename... _Types>
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::__access<
variant_alternative_t<_Np, variant<_Types...>>>(__v);
}
template<size_t _Np, typename... _Types>
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::__access<
variant_alternative_t<_Np, variant<_Types...>>>(std::move(__v));
}
template<typename _Visitor, typename... _Variants>
decltype(auto)
visit(_Visitor&& __visitor, _Variants&&... __variants)
{
using _Result_type =
decltype(forward<_Visitor>(__visitor)(get<0>(__variants)...));
static constexpr auto _S_vtable =
__detail::__variant::__gen_vtable<
_Result_type, _Visitor&&, _Variants&&...>::_S_apply();
auto __func_ptr = _S_vtable._M_access(__variants.index()...);
return (*__func_ptr)(forward<_Visitor>(__visitor),
__detail::__variant::__get_storage(__variants)...);
}
template<typename... _Types, typename _Alloc>
struct uses_allocator<variant<_Types...>, _Alloc>
: true_type { };
template<typename... _Types>
struct hash<variant<_Types...>>
{
using result_type = size_t;
using argument_type = variant<_Types...>;
size_t
operator()(const variant<_Types...>& __t) const
noexcept((... && noexcept(hash<decay_t<_Types>>{}(std::declval<_Types>()))))
{
if (!__t.valueless_by_exception())
{
namespace __edv = __detail::__variant;
static constexpr size_t (*_S_vtable[])(void*) =
{ &__edv::__erased_hash<const __edv::__storage<_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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