why it use void** here?

Question

the code pick up from v8-0.2.5

/**
 * Checks whether two handles are the same.
 * Returns true if both are empty, or if the objects
 * to which they refer are identical.
 * The handles' references are not checked.
 */
template <class S> bool operator==(Handle<S> that) {
  void** a = reinterpret_cast<void**>(**this);
  void** b = reinterpret_cast<void**>(*that);
  if (a == 0) return b == 0;
  if (b == 0) return false;
  return *a == *b;
}  

Handle Overload operator* so that **this and *that return type T*.

So it seems

  void* a = reinterpret_cast<void*>(**this);
  void* b = reinterpret_cast<void*>(*that);
  return a == b;

will also work well?

Answer 1

If a and b had type void*, then you couldn't dereference them (without casting them to something else first), so *a == *b wouldn't work.