Could somebody override this callBack()?

Could somebody override this callBack()?

Usually, callBack() gotta be overridden in Child class.
but it doesn't. When the thread calls callBack(), it runs original method.
Is there any way to right this?
I compiled it with "g++ -o file source.cpp -lpthread"
I'm sure it is not about a compiler.
#include <iostream>
#include <unistd.h>
#include <pthread.h>
using namespace std;
class Parent
{
public:
virtual void callBack()
{
cout << "Original callBack() reported this: " << this << endl;
}
private:
pthread_t th = 0;
static void *th_func(void *arg)
{
Parent *p = (Parent*)arg;
cout << "*th_func() reported *arg: " << arg << endl;
p->callBack();
}
public:
Parent()
{
if(pthread_create(&th, NULL, th_func, (void*)this) < 0)
cerr << "thread not born." << endl;
else
cout << "thread has born." << endl;
}
~Parent()
{
if(th!=0)
pthread_join(th, NULL);
cout << "joined. Parent leaving." << endl;
}
};
class Child : public Parent
{
public:
void callBack()
{
cout << "child overridden." << endl;
}
Child() : Parent(){}
};
int main()
{
Child *ch = new Child();
delete ch;
return 0;
}