Path: utzoo!mnetor!uunet!husc6!cmcl2!brl-adm!brl-smoke!gwyn
From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: comp.lang.c
Subject: Re: X3J11 meeting notes
Message-ID: <6866@brl-smoke.ARPA>
Date: 18 Dec 87 22:28:17 GMT
References: <6829@brl-smoke.ARPA> <406@mn-at1.UUCP> <6852@brl-smoke.ARPA> <13899@think.UUCP> <2149@ucbcad.berkeley.edu>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 13
Keywords: ANSI C standard

In article <2149@ucbcad.berkeley.edu> rudell@beeblebrox.UUCP (Richard Rudell) writes:
>	(a - 1) + 1
>The point is, ANSI never promised what might happen if 'a' was the most 
>positive integer.

No, as it now stands it is not legal for an ANSI C implementation to
introduce a (non-benign) overflow by rearranging an expression.
Although what happens on an overflow is undefined, it is not correct
to cause an overflow in violation of what the programmer actually
specified.  Thus, in the above example, if at run time `a' happens to
have the most negative possible value, an overflow is permitted (but
not required); however, for no other value of `a' is an overflow
permitted.