assigning an integer to the negation of ...

[Peter Desnoyers]

In article <15090 at mimsy.UUCP> chris at mimsy.UUCP (Chris Torek) writes:
>In article <1911 at pembina.UUCP> lake at alberta.UUCP (Robert Lake) writes:
>>		i = -(unsigned short)j;
>[where i is an int and j is 1---j's type is irrelevant]
>

It was pointed out that the context in which this problem arose was
TCP software - I would bet it was the window size calculations.
Quoting V. Jacobsen and R. Braden from RFC 1072 (TCP Extensions for
long-delay paths):

  The TCP header uses a 16 bit field to report the receive window size
  to the sender. Therefore, the largest window that can be used is 2**16
  = 65K bytes. (In practice, some TCP implementations will "break" for
  windows exceeding 2**15, because of their failure to do unsigned
  arithmetic.) 

I would also guess that the broken TCP implementations actually try to
do unsigned arithmetic, but don't get it right, as in the original,
subtly flawed example.

				Peter Desnoyers