gcc/testsuite/algol68/execute/loop-overflow-underflow.a68

{ Test for overflow/underflow in loops with implicit and explicit
  iterators. }

begin int count;

      { Overflow.  }
      count := 0;
      by 1 while true do count +:= 1 od;
      assert (count = max_int);

      count := 0;
      from max_int do count +:= 1 od;
      assert (count = 1);
      count := 0;

      by max_int do count +:= 1 od;
      assert (count = 1);

      count := 0;
      for i by max_int do count +:= 1 od;
      assert (count = 1);

      count := 0;
      by max_int % 2 do count +:= 1 od;
      assert (count = 3);

      count := 0;
      by max_int - 1 do count +:= 1 od;
      assert (count = 2);

      { Underflow.  }
      count := 0;
      by -1 while true do count +:= 1 od;
      assert (count = -min_int + 2);

      count := 0;
      from min_int by -1 do count +:= 1 od;
      assert (count = 1);
      count := 0;

      by min_int do count +:= 1 od;
      assert (count = 2);

      count := 0;
      for i by min_int do count +:= 1 od;
      assert (count = 2);

      count := 0;
      by min_int % 2 do count +:= 1 od;
      assert (count = 3);

      count := 0;
      by min_int + 1 do count +:= 1 od;
      assert (count = 2)
end