Question

We can call destructor explicitly through class pointer, why not constructor? Any idea?

#include <iostream>

class Con {
public:
    Con( int x ) : x( x ) {

    }

private:
    int x;
};

int main() {
    Con* c = new Con( 1 );
    //c->Con( 2 ); //illegal
    c->~Con(); // ok!
    delete c;
}

Thanks,

Answer 1

No. You cannot.

Con* c = new Con( 1 );
//c->Con( 2 ); //illegal

You’ve already called the constructor in the new expression.

By the time you’ve a valid pointer of type Con*, you’ve already created an object. And calling constructor on the “constructed” object doesn’t even make sense. So why would C++ allow that?