Unions within unions

Question

In C, is it possible to define a union within another union? If no, why is it not possible? Or if yes, where can it be used?

Answer 1

Suppose you want to define:

union myun {
  int x;
  sometype y;
};

where sometype is a typedef defined by a library you're using. If the library happened to implement it as a union type, then this would be a union within a union, and it would make sense because you can't (from a good design standpoint) violate the encapsulation of the library's type.