Re: Undefined reference to...

Problems with the above include

  * 'getLower' attempts to return an object of abstract class.

  * A local variable is declared with incomplete type 'Extended'.

  * If those obstacles weren't in the way, 'getLower' would perform
    a *slicing*, returning only the Base part of 'e', and then of type
    'Base'.

It's not clear what you're attempting, but it may be that you want a
Meyers' singleton:

  class Base
  {
  public:
      virtual void printOut() = 0;
      static Base& getLower();
  };

  class Extended: public Base
  {
  public:
      void printOut() { cout << "hello"; }
  };

  Base& Base::getLower()
  {
      static Extended e;
      // Whatever code you were intending to have here, then:
      return e;
  }

Note that with this scheme you always get the same object -- a singleton --
from 'getLower'.

Cheers & hth.,

- Alf