How to generate a compiler warning/error when object sliced

Question

I want to know if it is possible to let compiler issue a warning/error for code as following:

Note:

1. Yea, it is bad programming style and

Answer 1

class Derived: public Base{};

You're saying Derived IS a Base, and so it should work in any function that takes a base. If this is a real problem, maybe inheritance isn't what you really want to be using.

Answer 2

I modified your code slightly:

class Base{
  public:
    Base() {}
    explicit Base(const Base &) {}
};

class Derived: public Base {};

void Func(Base)
{

}

//void Func(Derived)
//{
//
//}

//main
int main() {
  Func(Derived());
}

The explicit keyword will make sure that the constructor will not be used as an implicit conversion operator - you have to call it explicitly when you want to use it.