incomplete types (was: Recursive #includes)

[Leo de Wit]

In article <9842 at smoke.BRL.MIL> gwyn at brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>) writes:
|There is nothing inherently "bad" about incomplete types, especially
|incomplete structure declarations.  In fact they are essential for
|declaring structures that contain pointers to each other.

How essential that is? Consider:

struct egg {
     struct hen {
          struct egg *eggp;
     } *henp;
};

This declares two structure types, each containing a pointer to the
other one. And I can give more complex examples (a nice one is the
grammar for the Bourne shell, which can be expressed in these type of
recursive data structures: essentially one big struct definition).

    Leo.