| Issue |
141648
|
| Summary |
[libc++] std::variant invokes move constructor of non-movable alternative in copy assignment
|
| Labels |
libc++
|
| Assignees |
|
| Reporter |
whess
|
Link to godbolt example: https://godbolt.org/z/r4as6sejq
```
struct CopyOnly {
explicit CopyOnly(const std::string& str) {}
CopyOnly(const CopyOnly&) = default;
CopyOnly(CopyOnly&&) = delete;
CopyOnly& operator=(const CopyOnly&) = default;
CopyOnly& operator=(CopyOnly&&) = delete;
std::string str;
};
int main() {
std::variant<std::string, CopyOnly> v;
std::variant<std::string, CopyOnly> v2;
v2 = v; // Compile error
return 0;
}
```
Compilation error:
```
In file included from <source>:1:
/opt/compiler-explorer/clang-14.0.0/bin/../include/c++/v1/variant:709:9: error: call to deleted constructor of 'std::__variant_detail::__alt<1, CopyOnly>::__value_type' (aka 'CopyOnly')
: __value(_VSTD::forward<_Args>(__args)...) {}
^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/clang-14.0.0/bin/../include/c++/v1/variant:877:9: note: in instantiation of function template specialization 'std::__variant_detail::__alt<1, CopyOnly>::__alt<CopyOnly>' requested here
__alt<_Ip, _Tp>(in_place, _VSTD::forward<_Args>(__args)...);
^
/opt/compiler-explorer/clang-14.0.0/bin/../include/c++/v1/variant:990:25: note: in instantiation of function template specialization 'std::__variant_detail::__ctor<std::__variant_detail::__traits<std::string, CopyOnly>>::__construct_alt<1UL, CopyOnly, CopyOnly>' requested here
auto& __res = this->__construct_alt(__access::__base::__get_alt<_Ip>(*this),
^
/opt/compiler-explorer/clang-14.0.0/bin/../include/c++/v1/variant:1003:7: note: in instantiation of member function 'std::__variant_detail::__assignment<std::__variant_detail::__traits<std::string, CopyOnly>>::__assign_alt(__alt<1UL, CopyOnly> &, const CopyOnly &)::(anonymous struct)::operator()' requested here
struct {
^
/opt/compiler-explorer/clang-14.0.0/bin/../include/c++/v1/variant:1029:19: note: in instantiation of function template specialization 'std::__variant_detail::__assignment<std::__variant_detail::__traits<std::string, CopyOnly>>::__assign_alt<1UL, CopyOnly, const CopyOnly &>' requested here
this->__assign_alt(
^
/opt/compiler-explorer/clang-14.0.0/bin/../include/c++/v1/variant:1108:13: note: in instantiation of function template specialization 'std::__variant_detail::__assignment<std::__variant_detail::__traits<std::string, CopyOnly>>::__generic_assign<const std::__variant_detail::__copy_assignment<std::__variant_detail::__traits<std::string, CopyOnly>, std::__variant_detail::_Trait::_Available> &>' requested here
this->__generic_assign(__that);
^
/opt/compiler-explorer/clang-14.0.0/bin/../include/c++/v1/variant:1119:28: note: in instantiation of member function 'std::__variant_detail::__copy_assignment<std::__variant_detail::__traits<std::string, CopyOnly>, std::__variant_detail::_Trait::_Available>::operator=' requested here
class _LIBCPP_TEMPLATE_VIS __impl
^
<source>:8:5: note: 'CopyOnly' has been explicitly marked deleted here
CopyOnly(CopyOnly&&) = delete;
^
1 error generated.
Compiler returned: 1
```
Compilation error does not occur in libstdc++. I'd expect this to compile without issue, invoking the copy constructor/assignment of the non-movable alternative where needed.
![]()
_______________________________________________
llvm-bugs mailing list
llvm-bugs@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
