[libcxx-commits] [libcxx] 057028e - Revert switch based variant temporarily.
Eric Fiselier via libcxx-commits
libcxx-commits at lists.llvm.org
Tue Sep 1 19:15:51 PDT 2020
Author: Eric Fiselier
Date: 2020-09-01T22:15:33-04:00
New Revision: 057028ed391f8b4bc029792fcca7771185b9da98
URL: https://github.com/llvm/llvm-project/commit/057028ed391f8b4bc029792fcca7771185b9da98
DIFF: https://github.com/llvm/llvm-project/commit/057028ed391f8b4bc029792fcca7771185b9da98.diff
LOG: Revert switch based variant temporarily.
There are currently some failures caused by this change internally. I'm working
to debug them and hopefully these series of patches should be recommitted by
the end of the week.
Thank you to Micheal Park for the contributions, and for allowing the temporary
rollback.
The commits reverted by this change are:
7d15ece79c16dc3237fc514ff56a69e3d58fbd39
e0ec7a02064968c7df11713689107148b4efb993
02197f7e50b938f8167b17b89bdf7c55feff4339
a175a96517c5d9dc05ba13a6481b1b031a53a22f
Added:
Modified:
libcxx/include/variant
Removed:
################################################################################
diff --git a/libcxx/include/variant b/libcxx/include/variant
index c58f0ac6a169..33d5dc7dbeb1 100644
--- a/libcxx/include/variant
+++ b/libcxx/include/variant
@@ -354,9 +354,9 @@ struct __valueless_t {};
enum class _Trait { _TriviallyAvailable, _Available, _Unavailable };
-template <class _Tp,
- template <class> class _IsTriviallyAvailable,
- template <class> class _IsAvailable>
+template <typename _Tp,
+ template <typename> class _IsTriviallyAvailable,
+ template <typename> class _IsAvailable>
constexpr _Trait __trait =
_IsTriviallyAvailable<_Tp>::value
? _Trait::_TriviallyAvailable
@@ -373,7 +373,7 @@ constexpr _Trait __common_trait(initializer_list<_Trait> __traits) {
return __result;
}
-template <class... _Types>
+template <typename... _Types>
struct __traits {
static constexpr _Trait __copy_constructible_trait =
__common_trait({__trait<_Types,
@@ -434,270 +434,183 @@ struct __variant {
namespace __visitation {
-#define _LIBCPP_VARIANT_CASES_4(_Case, _Base) \
- _Case(_Base + 0) \
- _Case(_Base + 1) \
- _Case(_Base + 2) \
- _Case(_Base + 3)
-
-#define _LIBCPP_VARIANT_CASES_16(_Case, _Base) \
- _LIBCPP_VARIANT_CASES_4(_Case, _Base + 4 * 0) \
- _LIBCPP_VARIANT_CASES_4(_Case, _Base + 4 * 1) \
- _LIBCPP_VARIANT_CASES_4(_Case, _Base + 4 * 2) \
- _LIBCPP_VARIANT_CASES_4(_Case, _Base + 4 * 3)
-
-#define _LIBCPP_VARIANT_CASES_64(_Case, _Base) \
- _LIBCPP_VARIANT_CASES_16(_Case, _Base + 16 * 0) \
- _LIBCPP_VARIANT_CASES_16(_Case, _Base + 16 * 1) \
- _LIBCPP_VARIANT_CASES_16(_Case, _Base + 16 * 2) \
- _LIBCPP_VARIANT_CASES_16(_Case, _Base + 16 * 3)
-
-#define _LIBCPP_VARIANT_CASES_256(_Case, _Base) \
- _LIBCPP_VARIANT_CASES_64(_Case, _Base + 64 * 0) \
- _LIBCPP_VARIANT_CASES_64(_Case, _Base + 64 * 1) \
- _LIBCPP_VARIANT_CASES_64(_Case, _Base + 64 * 2) \
- _LIBCPP_VARIANT_CASES_64(_Case, _Base + 64 * 3)
-
-#define _LIBCPP_VARIANT_CASES(_NumCases, _Case) \
- _LIBCPP_CONCAT(_LIBCPP_VARIANT_CASES_, _NumCases)(_Case, 0)
-
-#define _LIBCPP_VARIANT_SWITCH_MAX 256
-
-template <class _Iter, class _Fp, size_t... _Is>
-inline _LIBCPP_INLINE_VISIBILITY
-static constexpr void __fill_cartesian_impl(
- _Iter __iter, _Fp __f, index_sequence<_Is...>) {
- *__iter = __f(integral_constant<size_t, _Is>{}...);
-}
-
-template <class _Iter, class _Fp, size_t... _Is, size_t... _Js, class... _Ls>
-inline _LIBCPP_INLINE_VISIBILITY
-static constexpr void __fill_cartesian_impl(
- _Iter __iter, _Fp __f, index_sequence<_Is...>, index_sequence<_Js...>, _Ls... __ls) {
- constexpr size_t _Mp = (1 * ... * _Ls::size());
- (__fill_cartesian_impl(
- __iter + _Js * _Mp, __f, index_sequence<_Is..., _Js>{}, __ls...), ...);
-}
-
-template <size_t... _Ns, class _Iter, class _Fp>
-inline _LIBCPP_INLINE_VISIBILITY
-static constexpr void __fill_cartesian(_Iter __iter, _Fp __f) {
- __fill_cartesian_impl(
- __iter, __f, index_sequence<>{}, make_index_sequence<_Ns>{}...);
-}
-
-template <size_t _Np, size_t... _Ns>
-struct __multi {
+struct __base {
+ template <class _Visitor, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
- static constexpr size_t __size = (_Np * ... * _Ns);
+ static constexpr decltype(auto)
+ __visit_alt_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
+ constexpr auto __fdiagonal =
+ __make_fdiagonal<_Visitor&&,
+ decltype(_VSTD::forward<_Vs>(__vs).__as_base())...>();
+ return __fdiagonal[__index](_VSTD::forward<_Visitor>(__visitor),
+ _VSTD::forward<_Vs>(__vs).__as_base()...);
+ }
+ template <class _Visitor, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
- static constexpr size_t
- __index(const size_t (&__is)[sizeof...(_Ns) + 1]) noexcept {
- constexpr size_t __ns[] = {_Ns..., 1};
- size_t __result = 0;
- for (size_t __i = 0; __i < sizeof...(_Ns) + 1; ++__i) {
- if (__is[__i] == variant_npos) {
- return variant_npos;
- }
- __result += __is[__i];
- __result *= __ns[__i];
- }
- return __result;
+ static constexpr decltype(auto) __visit_alt(_Visitor&& __visitor,
+ _Vs&&... __vs) {
+ constexpr auto __fmatrix =
+ __make_fmatrix<_Visitor&&,
+ decltype(_VSTD::forward<_Vs>(__vs).__as_base())...>();
+ return __at(__fmatrix, __vs.index()...)(
+ _VSTD::forward<_Visitor>(__visitor),
+ _VSTD::forward<_Vs>(__vs).__as_base()...);
}
-};
-template <size_t... _Ns>
-struct __indices {
+private:
+ template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
- static constexpr auto __value = [] {
- using _Tp = array<size_t, sizeof...(_Ns)>;
- array<_Tp, (1 * ... * _Ns)> __result = {};
- __fill_cartesian<_Ns...>(__result.begin(),
- [](auto... __is) -> _Tp { return {__is...}; });
- return __result;
- }();
-};
+ static constexpr const _Tp& __at(const _Tp& __elem) { return __elem; }
-template <size_t... _Ns, class _Fp, class _Rp, class... _Args>
-inline _LIBCPP_INLINE_VISIBILITY
-static constexpr auto __make_vtable_impl(_Fp __f, _Rp (*)(_Args...)) {
- array<_Rp (*)(_Args...), (1 * ... * _Ns) + 1> __result = {
- [](_Args...) -> _Rp { __throw_bad_variant_access(); }
- };
- __fill_cartesian<_Ns...>(__result.begin() + 1, __f);
- return __result;
-}
+ template <class _Tp, size_t _Np, typename... _Indices>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto&& __at(const array<_Tp, _Np>& __elems,
+ size_t __index, _Indices... __indices) {
+ return __at(__elems[__index], __indices...);
+ }
-template <size_t... _Ns, class _Fp>
-inline _LIBCPP_INLINE_VISIBILITY
-static constexpr auto __make_vtable(_Fp __f) {
- using _Tp = decltype(__f(integral_constant<size_t, (_Ns, 0)>{}...));
- return __make_vtable_impl<_Ns...>(__f, _Tp{});
-}
+ template <class _Fp, class... _Fs>
+ static constexpr void __std_visit_visitor_return_type_check() {
+ static_assert(
+ __all<is_same_v<_Fp, _Fs>...>::value,
+ "`std::visit` requires the visitor to have a single return type.");
+ }
-struct __base {
- template <class _Vis, class... _Vs>
- struct __dispatch {
- template <size_t... _Is>
+ template <class... _Fs>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto __make_farray(_Fs&&... __fs) {
+ __std_visit_visitor_return_type_check<__uncvref_t<_Fs>...>();
+ using __result = array<common_type_t<__uncvref_t<_Fs>...>, sizeof...(_Fs)>;
+ return __result{{_VSTD::forward<_Fs>(__fs)...}};
+ }
+
+ template <std::size_t... _Is>
+ struct __dispatcher {
+ template <class _Fp, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
- constexpr auto operator()(integral_constant<size_t, _Is>...) const noexcept {
- return +[](_Vis&& __vis, _Vs&&... __vs) -> decltype(auto) {
+ static constexpr decltype(auto) __dispatch(_Fp __f, _Vs... __vs) {
return __invoke_constexpr(
- _VSTD::forward<_Vis>(__vis),
- __access::__base::__get_alt<_Is>(_VSTD::forward<_Vs>(__vs))...);
- };
+ static_cast<_Fp>(__f),
+ __access::__base::__get_alt<_Is>(static_cast<_Vs>(__vs))...);
}
};
- template <class _Vis, class _Vp, class _Wp>
+ template <class _Fp, class... _Vs, size_t... _Is>
inline _LIBCPP_INLINE_VISIBILITY
- static constexpr decltype(auto)
- __visit_alt_at(size_t __index, _Vis&& __vis, _Vp&& __v, _Wp&& __w) {
- constexpr size_t __size = __uncvref_t<_Vp>::__size();
- static_assert(__size == __uncvref_t<_Wp>::__size());
- constexpr auto __dispatch_at = [](auto __i) {
- return __dispatch<_Vis, _Vp, _Wp>{}(__i, __i);
- };
-#define _LIBCPP_VARIANT_CASE(_Ip) \
- case _Ip: { \
- if constexpr (_Ip < __size) { \
- return __dispatch_at(integral_constant<size_t, _Ip>{})( \
- _VSTD::forward<_Vis>(__vis), \
- _VSTD::forward<_Vp>(__v), \
- _VSTD::forward<_Wp>(__w)); \
- } else { \
- _LIBCPP_UNREACHABLE(); \
- } \
+ static constexpr auto __make_dispatch(index_sequence<_Is...>) {
+ return __dispatcher<_Is...>::template __dispatch<_Fp, _Vs...>;
}
- if constexpr (__size <= _LIBCPP_VARIANT_SWITCH_MAX) {
- switch (__index) {
- _LIBCPP_VARIANT_CASES(_LIBCPP_VARIANT_SWITCH_MAX, _LIBCPP_VARIANT_CASE)
- default: __throw_bad_variant_access();
- }
- } else {
- constexpr auto __vtable = __make_vtable<__size>(__dispatch_at);
- return __vtable[__index + 1](_VSTD::forward<_Vis>(__vis),
- _VSTD::forward<_Vp>(__v),
- _VSTD::forward<_Wp>(__w));
- }
-#undef _LIBCPP_VARIANT_CASE
+
+ template <size_t _Ip, class _Fp, class... _Vs>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto __make_fdiagonal_impl() {
+ return __make_dispatch<_Fp, _Vs...>(
+ index_sequence<(__identity<_Vs>{}, _Ip)...>{});
}
- template <size_t... _Is, class _Vis, class... _Vs>
+ template <class _Fp, class... _Vs, size_t... _Is>
inline _LIBCPP_INLINE_VISIBILITY
- static constexpr decltype(auto) __visit_alt(_Vis&& __vis, _Vs&&... __vs) {
- if constexpr (sizeof...(_Vs) == 0) {
- return __invoke_constexpr(_VSTD::forward<_Vis>(__vis));
- } else {
- return __visit_alt_impl(index_sequence_for<_Vs...>{},
- _VSTD::forward<_Vis>(__vis),
- _VSTD::forward<_Vs>(__vs)...);
- }
+ static constexpr auto __make_fdiagonal_impl(index_sequence<_Is...>) {
+ return __base::__make_farray(__make_fdiagonal_impl<_Is, _Fp, _Vs...>()...);
}
- template <size_t... _Is, class _Vis, class... _Vs>
+ template <class _Fp, class _Vp, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
- static constexpr decltype(auto)
- __visit_alt_impl(index_sequence<_Is...>, _Vis&& __vis, _Vs&&... __vs) {
- using __multi = __multi<__uncvref_t<_Vs>::__size()...>;
- constexpr __dispatch<_Vis, _Vs...> __dispatch;
-#define _LIBCPP_VARIANT_CASE(_Ip) \
- case _Ip: { \
- if constexpr (_Ip < __multi::__size) { \
- return __dispatch(integral_constant<size_t, __itable[_Ip][_Is]>{}...)( \
- _VSTD::forward<_Vis>(__vis), _VSTD::forward<_Vs>(__vs)...); \
- } else { \
- _LIBCPP_UNREACHABLE(); \
- } \
+ static constexpr auto __make_fdiagonal() {
+ constexpr size_t _Np = __uncvref_t<_Vp>::__size();
+ static_assert(__all<(_Np == __uncvref_t<_Vs>::__size())...>::value);
+ return __make_fdiagonal_impl<_Fp, _Vp, _Vs...>(make_index_sequence<_Np>{});
}
- if constexpr (__multi::__size <= _LIBCPP_VARIANT_SWITCH_MAX) {
- constexpr const auto& __itable =
- __indices<__uncvref_t<_Vs>::__size()...>::__value;
- switch (__multi::__index({__vs.index()...})) {
- _LIBCPP_VARIANT_CASES(_LIBCPP_VARIANT_SWITCH_MAX, _LIBCPP_VARIANT_CASE)
- default: __throw_bad_variant_access();
- }
- } else {
- constexpr auto __vtable =
- __make_vtable<__uncvref_t<_Vs>::__size()...>(__dispatch);
- return __vtable[__multi::__index({__vs.index()...}) + 1](
- _VSTD::forward<_Vis>(__vis), _VSTD::forward<_Vs>(__vs)...);
- }
-#undef _LIBCPP_VARIANT_CASE
+
+ template <class _Fp, class... _Vs, size_t... _Is>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto __make_fmatrix_impl(index_sequence<_Is...> __is) {
+ return __make_dispatch<_Fp, _Vs...>(__is);
+ }
+
+ template <class _Fp, class... _Vs, size_t... _Is, size_t... _Js, class... _Ls>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto __make_fmatrix_impl(index_sequence<_Is...>,
+ index_sequence<_Js...>,
+ _Ls... __ls) {
+ return __base::__make_farray(__make_fmatrix_impl<_Fp, _Vs...>(
+ index_sequence<_Is..., _Js>{}, __ls...)...);
+ }
+
+ template <class _Fp, class... _Vs>
+ inline _LIBCPP_INLINE_VISIBILITY
+ static constexpr auto __make_fmatrix() {
+ return __make_fmatrix_impl<_Fp, _Vs...>(
+ index_sequence<>{}, make_index_sequence<__uncvref_t<_Vs>::__size()>{}...);
}
};
struct __variant {
- template <class _Vis, class _Vp, class _Wp>
+ template <class _Visitor, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr decltype(auto)
- __visit_alt_at(size_t __index, _Vis&& __vis, _Vp&& __v, _Wp&& __w) {
+ __visit_alt_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
return __base::__visit_alt_at(__index,
- _VSTD::forward<_Vis>(__vis),
- _VSTD::forward<_Vp>(__v).__impl,
- _VSTD::forward<_Wp>(__w).__impl);
+ _VSTD::forward<_Visitor>(__visitor),
+ _VSTD::forward<_Vs>(__vs).__impl...);
}
- template <class _Vis, class... _Vs>
+ template <class _Visitor, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
- static constexpr decltype(auto) __visit_alt(_Vis&& __vis, _Vs&&... __vs) {
- return __base::__visit_alt(_VSTD::forward<_Vis>(__vis),
+ static constexpr decltype(auto) __visit_alt(_Visitor&& __visitor,
+ _Vs&&... __vs) {
+ return __base::__visit_alt(_VSTD::forward<_Visitor>(__visitor),
_VSTD::forward<_Vs>(__vs).__impl...);
}
- template <class _Vis, class _Vp, class _Wp>
+ template <class _Visitor, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
static constexpr decltype(auto)
- __visit_value_at(size_t __index, _Vis&& __vis, _Vp&& __v, _Wp&& __w) {
- return __visit_alt_at(__index,
- __make_value_visitor(_VSTD::forward<_Vis>(__vis)),
- _VSTD::forward<_Vp>(__v),
- _VSTD::forward<_Wp>(__w));
+ __visit_value_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
+ return __visit_alt_at(
+ __index,
+ __make_value_visitor(_VSTD::forward<_Visitor>(__visitor)),
+ _VSTD::forward<_Vs>(__vs)...);
}
- template <class _Vis, class... _Vs>
+ template <class _Visitor, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
- static constexpr decltype(auto) __visit_value(_Vis&& __vis, _Vs&&... __vs) {
- return __visit_alt(__make_value_visitor(_VSTD::forward<_Vis>(__vis)),
- _VSTD::forward<_Vs>(__vs)...);
+ static constexpr decltype(auto) __visit_value(_Visitor&& __visitor,
+ _Vs&&... __vs) {
+ return __visit_alt(
+ __make_value_visitor(_VSTD::forward<_Visitor>(__visitor)),
+ _VSTD::forward<_Vs>(__vs)...);
}
private:
- template <class _Vis, class... _Values>
- inline _LIBCPP_INLINE_VISIBILITY
+ template <class _Visitor, class... _Values>
static constexpr void __std_visit_exhaustive_visitor_check() {
- static_assert(is_invocable_v<_Vis, _Values...>,
+ static_assert(is_invocable_v<_Visitor, _Values...>,
"`std::visit` requires the visitor to be exhaustive.");
}
- template <class _Vis>
+ template <class _Visitor>
struct __value_visitor {
template <class... _Alts>
inline _LIBCPP_INLINE_VISIBILITY
constexpr decltype(auto) operator()(_Alts&&... __alts) const {
__std_visit_exhaustive_visitor_check<
- _Vis, decltype((_VSTD::forward<_Alts>(__alts).__value))...>();
- return __invoke_constexpr(_VSTD::forward<_Vis>(__vis),
+ _Visitor,
+ decltype((_VSTD::forward<_Alts>(__alts).__value))...>();
+ return __invoke_constexpr(_VSTD::forward<_Visitor>(__visitor),
_VSTD::forward<_Alts>(__alts).__value...);
}
- _Vis&& __vis;
+ _Visitor&& __visitor;
};
- template <class _Vis>
+ template <class _Visitor>
inline _LIBCPP_INLINE_VISIBILITY
- static constexpr auto __make_value_visitor(_Vis&& __vis) {
- return __value_visitor<_Vis>{_VSTD::forward<_Vis>(__vis)};
+ static constexpr auto __make_value_visitor(_Visitor&& __visitor) {
+ return __value_visitor<_Visitor>{_VSTD::forward<_Visitor>(__visitor)};
}
};
-#undef _LIBCPP_VARIANT_SWITCH_MAX
-#undef _LIBCPP_VARIANT_CASES
-#undef _LIBCPP_VARIANT_CASES_256
-#undef _LIBCPP_VARIANT_CASES_64
-#undef _LIBCPP_VARIANT_CASES_16
-#undef _LIBCPP_VARIANT_CASES_4
-
} // namespace __visitation
template <size_t _Index, class _Tp>
@@ -720,7 +633,7 @@ union _LIBCPP_TEMPLATE_VIS __union<_DestructibleTrait, _Index> {};
#define _LIBCPP_VARIANT_UNION(destructible_trait, destructor) \
template <size_t _Index, class _Tp, class... _Types> \
- union _LIBCPP_TEMPLATE_VIS __union<destructible_trait, \
+ union _LIBCPP_TEMPLATE_VIS __union<destructible_trait, \
_Index, \
_Tp, \
_Types...> { \
@@ -874,9 +787,9 @@ protected:
template <size_t _Ip, class _Tp, class... _Args>
inline _LIBCPP_INLINE_VISIBILITY
static _Tp& __construct_alt(__alt<_Ip, _Tp>& __a, _Args&&... __args) {
- auto* __result = ::new ((void*)_VSTD::addressof(__a))
+ ::new ((void*)_VSTD::addressof(__a))
__alt<_Ip, _Tp>(in_place, _VSTD::forward<_Args>(__args)...);
- return __result->__value;
+ return __a.__value;
}
template <class _Rhs>
@@ -903,7 +816,7 @@ class _LIBCPP_TEMPLATE_VIS __move_constructor;
#define _LIBCPP_VARIANT_MOVE_CONSTRUCTOR(move_constructible_trait, \
move_constructor) \
template <class... _Types> \
- class _LIBCPP_TEMPLATE_VIS __move_constructor<__traits<_Types...>, \
+ class _LIBCPP_TEMPLATE_VIS __move_constructor<__traits<_Types...>, \
move_constructible_trait> \
: public __constructor<__traits<_Types...>> { \
using __base_type = __constructor<__traits<_Types...>>; \
@@ -943,7 +856,7 @@ class _LIBCPP_TEMPLATE_VIS __copy_constructor;
#define _LIBCPP_VARIANT_COPY_CONSTRUCTOR(copy_constructible_trait, \
copy_constructor) \
template <class... _Types> \
- class _LIBCPP_TEMPLATE_VIS __copy_constructor<__traits<_Types...>, \
+ class _LIBCPP_TEMPLATE_VIS __copy_constructor<__traits<_Types...>, \
copy_constructible_trait> \
: public __move_constructor<__traits<_Types...>> { \
using __base_type = __move_constructor<__traits<_Types...>>; \
@@ -989,7 +902,7 @@ public:
auto& __emplace(_Args&&... __args) {
this->__destroy();
auto& __res = this->__construct_alt(__access::__base::__get_alt<_Ip>(*this),
- _VSTD::forward<_Args>(__args)...);
+ _VSTD::forward<_Args>(__args)...);
this->__index = _Ip;
return __res;
}
@@ -1042,7 +955,7 @@ class _LIBCPP_TEMPLATE_VIS __move_assignment;
#define _LIBCPP_VARIANT_MOVE_ASSIGNMENT(move_assignable_trait, \
move_assignment) \
template <class... _Types> \
- class _LIBCPP_TEMPLATE_VIS __move_assignment<__traits<_Types...>, \
+ class _LIBCPP_TEMPLATE_VIS __move_assignment<__traits<_Types...>, \
move_assignable_trait> \
: public __assignment<__traits<_Types...>> { \
using __base_type = __assignment<__traits<_Types...>>; \
@@ -1083,7 +996,7 @@ class _LIBCPP_TEMPLATE_VIS __copy_assignment;
#define _LIBCPP_VARIANT_COPY_ASSIGNMENT(copy_assignable_trait, \
copy_assignment) \
template <class... _Types> \
- class _LIBCPP_TEMPLATE_VIS __copy_assignment<__traits<_Types...>, \
+ class _LIBCPP_TEMPLATE_VIS __copy_assignment<__traits<_Types...>, \
copy_assignable_trait> \
: public __move_assignment<__traits<_Types...>> { \
using __base_type = __move_assignment<__traits<_Types...>>; \
@@ -1677,12 +1590,18 @@ constexpr bool operator>=(const variant<_Types...>& __lhs,
__lhs.index(), __convert_to_bool<greater_equal<>>{}, __lhs, __rhs);
}
-template <class _Vis, class... _Vs>
+template <class _Visitor, class... _Vs>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS
-constexpr decltype(auto) visit(_Vis&& __vis, _Vs&&... __vs) {
+constexpr decltype(auto) visit(_Visitor&& __visitor, _Vs&&... __vs) {
using __variant_detail::__visitation::__variant;
- return __variant::__visit_value(_VSTD::forward<_Vis>(__vis),
+ bool __results[] = {__vs.valueless_by_exception()...};
+ for (bool __result : __results) {
+ if (__result) {
+ __throw_bad_variant_access();
+ }
+ }
+ return __variant::__visit_value(_VSTD::forward<_Visitor>(__visitor),
_VSTD::forward<_Vs>(__vs)...);
}
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