Initializer list for struct deriving from class (C )-CodePudding

Can you tell me what is wrong in the following example? I am using C 17, where I thought the following should be supported.

class Base {
public:
    virtual ~Base() = default;
};

struct Derived : public Base {
    int m1;
};

int main() {
    /* Results in a compilation error 
     * error C2440: 'initializing': cannot convert from 'initializer list' to 'Derived'
     * message : No constructor could take the source type, or constructor overload resolution was ambiguous */
    Derived d{ {},1 };
    return 0;
}

CodePudding user response：

It does not work because Derived is not an aggregate since it has a base class with virtual members.

The code compiles and runs when removing the virtual destructor in Base and using C 17.

If Base requires a virtual destructor, Derived can implement a custom constructor allowing initialization using curly brackets.

class Base {
public:
    virtual ~Base() = default;
};

struct Derived : public Base {
    Derived(int m): m1(m) {}
    int m1;
};

int main() {
    Derived d{ 1 };
    return 0;
}