If classes with virtual functions are implemented with vtables, how is a class with no virtual functions implemented?

struct A
{
  void foo ();
  void bar () const;
};

struct A
{
};

void foo (A * this);
void bar (A const * this);

struct A
{
  virtual void foo ();
};

void foo (A * this) {
  void (*realFoo)(A *) = lookupVtable (this->vtable, "foo");
  (realFoo)(this);   // Make the call to the most derived version of 'foo'
}

void CMyThingy::DoSomething(int arg);
{
    // do something
}

void CMyThingy_DoSomething(CMyThingy* this, int arg)
{
    /do something
}

myObj.doSomething(aValue);

CMyThingy_DoSomething(&myObj, aValue);