Re: Can an object know it is dead?

With my solution, an assert will fire if some part of the code attempts
to destroy an object that is in use. I agree though that it allows one
to attempt to use an object that was destroyed and that needs to be
fixed. Here is a revised version:

map<void*, size_t> lock;

class Object {
   Object() {
      assert( lock.find(this) == lock.end() );
      lock[this] = 0;
   }
   ~Object() {
      assert( lock[this] == 0 );
      lock.erase( this );
   }

   void func() {
      assert( lock.find(this) != lock.end() );
      ++lock[this];
      // do work
      --lock[this];
   }
};

void user( Object* o ) {
   assert( lock.find(o) != lock.end() );
   ++lock[o];
   // work with 'o'
   --lock[o];
}

With the above, if you attempt to destroy an object that is still being
used by someone, an assert will fire and if you attempt to create an
object in a memory location that is in use, an assert will fire.

Of course it is wise to wrap the increment and decrement in an object
(RAII)

class Locker {
   const void* obj;
   Locker( const void* obj ): obj(obj) {
      assert( lock.find(obj) != lock.end() );
      ++lock[obj];
   }
   ~Locker() {
      --lock[obj];
   }
};