1 struct priv; 2 typedef struct priv* priv_ptr; 3 4 #define NULL (void*)0 5 6 struct S 7 { 8 priv_ptr p; 9 }; 10 11 typedef struct S* s_ptr; 12 13 void 14 foo(s_ptr, int a); 15 16 s_ptr 17 bar(s_ptr, char a); 18 19 void 20 baz(s_ptr); 21