gcc/testsuite/gcc.dg/pr51957-1.h

   1 union R { int c; union R *p; };
   2 extern union R *w[];
   3 typedef struct { int t; } T;
   4 typedef struct { void *u; } U;
   5 union R *fn1 (void);
   6 void fn2 (int, const char *, union R *);
   7 void fn3 (void);
   8 int fn4 (union R *);
   9 void foo (U *x);