member function pointers with mysterious superclass

mfn_superclass.cpp

#include <iostream>
#include <pthread.h>

/** Calling a member function using a mysterious superclass */

#include <stdio.h>

class Super;
typedef void* (Super::*pSuperMF)(void*);

// class Launcher exists as a container of an instance and an argument.
// Using templates allows us to use the Launcher for a member of any class
template <class T>
class Launcher {
public:
  Launcher(T* _o, pSuperMF _f, void* _arg) : o(_o), f(_f), arg(_arg) {}
  void* launch() {
    return (o->*f)(arg);
  }
  T* o;
  void* a;
  pSuperMF f;
  void* arg;
};

// a function with happily external linkage, which we will pass to
// pthread_create instead of the (internal) member function
template <class T>
void* LaunchMember(void* o) {
    Launcher<T>* l = reinterpret_cast<Launcher<T>* >(o);
    return l->launch();
}

class Bar {
public:
  Bar() : i(0) {}
  int i;
};

class Super {
public:
  virtual void* threadMe(void* arg) {
    std::cout << "Super::threadMe" << std::endl;
  }
};

class Foo : public Super {
public:
  Foo();
  void* threadMe(void* arg);
private:
  pthread_t fThread;
  Bar bar;
};

Foo::Foo() {
  bar.i = 42;
  int arg = 12;
  Launcher<Super> l(this, &Super::threadMe, (void*)&arg);
  pthread_create(&fThread, NULL, LaunchMember<Super>, &l);
  pthread_join(fThread, NULL);
}

void* Foo::threadMe(void* arg) {
  std::cout << "Foo::threadMe: *arg = " << *((int*)(arg)) << std::endl;
  std::cout << "Foo::threadMe: bar.i = " << bar.i << std::endl;
}

int main(int argc, char* argv[]) {
  Foo* f = new Foo();
  return 0;
}