https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77641
Bug ID: 77641
Summary: std::variant copy-initialization fails for non-trivial
literal type
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Keywords: rejects-valid
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
CC: timshen at gcc dot gnu.org
Target Milestone: ---
#include <variant>
struct X {
constexpr X() { }
};
int main() {
std::variant<X> v1 = X{};
}
In file included from v.cc:1:0:
/home/jwakely/gcc/7/include/c++/7.0.0/variant: In instantiation of
‘std::__detail::__variant::_Variant_base<_Types>::_Variant_base(std::__detail::__variant::_Variant_base<_Types>&&)
[with _Types = {X}]’:
/home/jwakely/gcc/7/include/c++/7.0.0/variant:995:7: required from here
/home/jwakely/gcc/7/include/c++/7.0.0/variant:369:44: error: use of deleted
function ‘std::__detail::__variant::_Variant_storage<_First, _Rest
...>::_Variant_storage() [with _First = X; _Rest = {}]’
: _Storage(), _M_index(__rhs._M_index)
^
/home/jwakely/gcc/7/include/c++/7.0.0/variant:297:17: note:
‘std::__detail::__variant::_Variant_storage<_First, _Rest
...>::_Variant_storage() [with _First = X; _Rest = {}]’ is implicitly deleted
because the default definition would be ill-formed:
constexpr _Variant_storage() = default;
^~~~~~~~~~~~~~~~
/home/jwakely/gcc/7/include/c++/7.0.0/variant:321:36: error: union member
‘std::__detail::__variant::_Variant_storage<X>::<unnamed union>::_M_first’ with
non-trivial ‘constexpr std::__detail::__variant::_Uninitialized<_Type,
true>::_Uninitialized() [with _Type = X]’
_Uninitialized<__storage<_First>> _M_first;
^~~~~~~~
/home/jwakely/gcc/7/include/c++/7.0.0/variant: In instantiation of ‘constexpr
void std::__detail::__variant::__erased_ctor(void*, void*) [with _Lhs = X&;
_Rhs = X&&]’:
/home/jwakely/gcc/7/include/c++/7.0.0/variant:373:30: required from
‘std::__detail::__variant::_Variant_base<_Types>::_Variant_base(std::__detail::__variant::_Variant_base<_Types>&&)
[with _Types = {X}]’
/home/jwakely/gcc/7/include/c++/7.0.0/variant:995:7: required from here
/home/jwakely/gcc/7/include/c++/7.0.0/variant:239:58: error: use of
‘decltype(auto) std::__detail::__variant::__get_alternative(void*) [with
_Qualified_storage = X&&]’ before deduction of ‘auto’
{ ::new (__lhs) decay_t<_Lhs>(__get_alternative<_Rhs>(__rhs)); }
~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
