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class Base {
public:
    virtual ~Base () {}
    virtual void run () = 0;

# include "Base.h"

class Derived: public Base {
public:
    Derived () {buf_[0] = 'a';}
    void run () {buf_[0] = 'z';}
    char buf_[1];
};

void runModule () {
    Derived a, b;
    Base *pa = &a, *pb = &b;
    pb->run ();  // Expect b.buf_[0] == 'z'
    pa->run ();  // Expect a.buf_[0] == 'z'
}

# include "Base.h"

class Attacker: public Base {
public: void run () {
        // vtable is overwritten
        // do malicious things here
        // ...
    }
}

class Derived: public Base {  // Class violating ODR
public:
    void run () {
        buf_[0] = 'z';  // Looks normal, but ...
        Attacker x;  // Instantiate to get a vtable to inject
        *((unsigned *)(buf_ + 12)) = *((const unsigned *)(&x));
    }
    char buf_[16];  // Buffer used to overwrite vtable
};

Derived d;  // Instantiate to get malicious Derived