Re: Implementation of abstract classes

I have some classes which are derived from some base:

class base {
  void foo();
  void bar();
};

class a : public base {
};

class b: public base{
};

The problem is as follows:

1) I would like to prevent users from making instances of
   class base
2) There are no overloaded functions beween the base class
   and the derived classes, so I can not use the usual

   virtual void overloaded_function() = 0;

   in the base class.

As far as I can see, there are two ways to proceed:

1) make some virtual dummy function that the
   derived classes need to implement
2) Hide the constructor of base as protected.

From a semantic point of view the latter solution
seems the more elegant. Is this a good solution
or are there traps or snags associated with it?