https://en.cppreference.com/w/cpp/language/inline
隐式生成的成员函数和任何成员函数
在类定义中定义的任何其他函数。
// header file
// OK, implicit inline
struct A {
~A() {}
};
// header file
// OK, implicit inline
struct A {
~A() = default;
};
// header file
struct A {
~A();
};
// NOT ok, ODR violation when header is included in more than 1 TU
A::~A() {};
// header file
struct A {
~A();
};
// NOT ok, ODR violation when header is included in more than 1 TU
A::~A() = default;