Unexpected deceitfulness of default parameters or my language is my enemy

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#include <iostream>
using namespace std;

class A {
public:
    virtual void Foo (int n = 10) {
        cout << "A::Foo, n = " << n << endl;
    }
};

class B : public A {
public:
    virtual void Foo (int n = 20) {
        cout << "B::Foo, n = " << n << endl;
    }
};

int main() {
    A * pa = new B ();
    pa->Foo ();

    return 0;
}

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B::Foo, n = 10

, B::Foo, n = 20, . , ?! , , B. … …

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— §8.3.6, 10 working paper ISO/IEC 14882: Programming Language C++. ( working paper . 1998 .)

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P.S. , no_smoking . !