gcc/testsuite/algol68/execute/undefined-1.a68

# { dg-options "-fstropping=upper" }  #
# j's value is undefined (defined to be 0 in GNU Algol)  #
BEGIN INT x := 0;
      FOR i TO 5
      DO ASSERT (j = 0);
         IF j > 20 THEN stop FI;
         INT j = x + i;
         x +:= 1
      OD
END