If the destructor isn't implemented in derived classes, they will use the parent's destructor. Not a guaranteed memory leak..... but something you need to be aware of.
class Base {
public:
Base() {}
~Base() {}
};
class Derived : public Base {
private:
Foo* _foo;
public:
Derived() : _foo(new Foo) {}
~Derived() { delete _foo; }
};
int main() {
std::unique_ptr<Base>(new Derived);
}