Question

Is there a way to avoid copying large vectors, when a function expects a vector with (pointer to) baseclass objects as input but I only have a vector of (pointers to) derived objects?

class Base {};

class Derived : public Base {};

void doStuff(vector<Base*> &vec)
{
    //do stuff with vec objects
}

int main()
{
    vector<Derived*> fooDerived(1000000);

    vector<Base*> fooBase(fooDerived.begin(), fooDerived.end()); // how to avoid copying here?
    doStuff(fooBase);
}

Answer 1

If you could use a vector<Derived*> as if it where a vector<Base*>, you could add a pointer to a class OtherDerived : public Base to that vector. This would be dangerous.