#include <iostream>
 
using namespace std;
 
class B;
void f( const B& b );
 
class B
{
    friend void f( const B& b );  
    int p = 42;    
    virtual int getP() const { return p; }
};
 
class D : public B
{
    virtual int getP() const { return p; }
    int p = 100500;
};
 
void f( const B& b )
{
    cout << b.getP() << endl;
    //cout << dynamic_cast<const D&>(b).getP() << endl; // так уже нельзя
}
 
int main() {
    B b;
    f( b );
 
    D d;
    f( d );
 
	return 0;
}

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