I have run into a problem that a move constructor of a superclass did not get invoked properly when its subclass has an explicitly defaulted destructor. The move constructor does get invoked when the destructor is implicitly defaulted (not provided at all in the supclass definition).
I am aware of the [constraints(Explicitly defaulted move constructor) that the compilers should apply to default move constructors. Yet, I have been by all means sure that the compiler should not discriminates between explicitly/implicitly defaulted destructors (or constructors as well) when applying these rules. In other words, explicitly defaulted destructor should not be treated as user-defined one (in contrast to an “empty” user-defined destructor ).
Tested with MSVC 2019 only.
Am I or MSVC right here?
#include <iostream>
class A {
public:
A() = default;
A(const A&) { std::cout << "Auch, they'r making copy of me(?!)" << std::endl; }
A(A&&) { std::cout << "I am moving :)" << std::endl; }
~A() = default;
};
class B : public A {
public:
};
class C : public A {
public:
C() = default;
};
class D : public A {
public:
~D() = default;
};
class E : public A {
public:
E() = default;
E(const E&) = default;
E(E&&) = default;
~E() = default;
};
int main()
{
std::cout << "\n---- A ----\n" << std::endl;
A a;
A a2(std::move(a));
std::cout << "\n---- B ----\n" << std::endl;
B b;
B b2(std::move(b));
std::cout << "\n---- C ----\n" << std::endl;
C c;
C c2(std::move(c));
std::cout << "\n---- D ----\n" << std::endl;
D d;
D d2(std::move(d));
std::cout << "\n---- E ----\n" << std::endl;
E e;
E e2(std::move(e));
}
EXPECTED: Display "I am moving :)" in all cases ACTUAL: Displays "Auch, they'r making copy of me(?!)" in case D
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