https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107598
Bug ID: 107598
Summary: implicitly-defined copy/move assignment op not
constexpr
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: mpolacek at gcc dot gnu.org
Target Milestone: ---
The following test is rejected with:
bug1.C: In function ‘constexpr void g()’:
bug1.C:11:7: error: call to non-‘constexpr’ function ‘S& S::operator=(const
S&)’
11 | b = a;
| ^
bug1.C:5:4: note: ‘S& S::operator=(const S&)’ is not usable as a ‘constexpr’
function because:
5 | S& S::operator=(const S&) = default;
| ^
...because what?
I think it should be accepted, at least in C++23, because
[class.copy.assign]/10:
"A copy/move assignment operator for a class X that is defaulted and not
defined as deleted is implicitly defined when it is odr-used ([basic.def.odr])
(e.g., when it is selected by overload resolution to assign to an object of its
class type), when it is needed for constant evaluation ([expr.const]), or when
it is explicitly defaulted after its first declaration.
The implicitly-defined copy/move assignment operator is constexpr."
Here it is explicitly defaulted after its first declaration.
struct S {
constexpr S() {}
S& operator=(const S&);
};
S& S::operator=(const S&) = default;
constexpr void
g ()
{
S a, b;
b = a;
}
