https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94061
Bug ID: 94061
Summary: defaulted member operator <=> defined as deleted if a
base has protected member operator <=>
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: okannen at gmail dot com
Target Milestone: ---
Version: GCC 10.0.1 20200229
When a base class declares the three way comparison member operator as
protected, a defaulted three way comparison member operator in the derived is
defined as deleted, while it shall obviously not:
Code:
#include <compare>
struct A{
protected:
auto operator <=> (const A&) const = default;
};
struct B
: A
{
auto operator <=> (const B&) const = default;
};
void f(B b){
b <=> b; //error see bellow
}
Error message:
<source>: In function 'void f(B)':
<source>:15:11: error: use of deleted function 'constexpr auto
B::operator<=>(const B&) const'
15 | b <=> b;
| ^
<source>:11:10: note: 'constexpr auto B::operator<=>(const B&) const' is
implicitly deleted because the default definition would be ill-formed:
11 | auto operator <=> (const B&) const = default;
| ^~~~~~~~
<source>:11:10: error: 'auto A::operator<=>(const A&) const' is protected
within this context
<source>:5:10: note: declared protected here
5 | auto operator <=> (const A&) const = default;
| ^~~~~~~~
Compiler returned: 1
