union

// Example is from POSIX
union sigval {
    int     sival_int;
    void   *sival_ptr;
};

union foo; // elaborated type specifier -> forward declaration
class bar {
  public:
    bar(foo& f);
};
void baz();
union baz; // another elaborated type specifer; another forward declaration
           // note: the class has the same name as the function void baz()
union foo {
    long l;
    union baz* b; // elaborated type specifier refers to the class,
                  // not the function of the same name
};