VR_RANGE with inverted bounds

[Martin Sebor <msebor at gmail dot com>]

While processing the (p += i) expression below to validate the bounds
of the pointer in I call get_range_info for i (in tree-object-size.c).
The function returns the following VR_RANGE: [2147483648, -2147483649]
rather than the expected [0, 1].  Is such a range to be expected or
is it a bug?

In general, what assumptions can I safely make about the bounds for
VR_RANGE and VR_ANTI_RANGE?  For example, besides being inverted like
in this example, can the bounds also ever be the same?  I don't think
I have seen them be the same but I think I have seen a case where the
variable's effective range was [X, X] (i.e., it was equal to
a constant) and get_range_info returned VR_VARYING.  Should that also
be expected?

Thanks
Martin

  void g (char *p, int i)
  {
    if (i < 0 || 1 < i)
      i = 0;

    p += i;
    ...
  }