Path: utzoo!utgpu!water!watmath!clyde!rutgers!cmcl2!brl-adm!umd5!ames!pasteur!ucbvax!hplabs!decwrl!labrea!glacier!jbn
From: jbn@glacier.STANFORD.EDU (John B. Nagle)
Newsgroups: comp.lang.c
Subject: Re: Another way (How not to write a loop)
Message-ID: <17319@glacier.STANFORD.EDU>
Date: 20 Feb 88 19:15:17 GMT
References: <560@naucse.UUCP> <1988Feb11.200149.25172@sq.uucp> <2115@bsu-cs.UUCP> <7278@brl-smoke.ARPA> <2049@rti.UUCP>
Reply-To: jbn@glacier.UUCP (John B. Nagle)
Organization: Stanford University
Lines: 13


     Another classic problem is the fact that the difference between two
unsigned values is itself unsigned.  Thus,

     unsigned short a,b; 

     a = 1;
     b = 2;
     if (a - b < 0) printf("B smaller than A\n"); 

is invalid.  This particular strangeness caused an obscure bug in 4.3BSD
networking which prevented interoperation of 4.3BSD's TCP with some
other TCP implementations, including TOPS-20.