#include <stdio.h>
#include <stdint.h>


typedef void** VTABLE;


struct Foo {
    virtual void
    bar() {
        printf("Hello\n");
    }
};


void
patchedBar(Foo* foo) {
    printf("Patched\n");
}


int
main(int argc, char *argv[]) {
  Foo* foo = new Foo();
  VTABLE vtable = *(VTABLE*)foo;

  foo->bar();

  void (Foo::* ptr)() = &Foo::bar;
  void* offset = *(VTABLE)&ptr;
  vtable[((uintptr_t)offset)/sizeof(void*)] = (void*)&patchedBar;

  foo->bar();

  return 0;
}