// `0x123` means the address of the object.

weakref<X> active(0x123);
free(0x123);     // cache.push_back(0x123)  And weakflag.Set(true)
0x123 = alloc(); // 0x123 = cache.pop_back()
weakref<X> tmp(0x123);

active = tmp; // Assignment is not executed because it is the following code

// weakref.cpp: ::operator =(const CScriptWeakRef &other)
//     // Don't do anything if it is the same reference
//     if( m_ref == other.m_ref )
//       return *this;

if( active.get() is null ) {
  println("is null!!!!");
}