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From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: comp.lang.c
Subject: Re: pointer arithmetic question
Message-ID: <6580@brl-smoke.ARPA>
Date: Mon, 19-Oct-87 08:39:24 EDT
Article-I.D.: brl-smok.6580
Posted: Mon Oct 19 08:39:24 1987
Date-Received: Tue, 20-Oct-87 02:07:00 EDT
References: <0.21787448@milehi>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 8

In article <0.21787448@milehi> Ray_Gardner@milehi (Ray Gardner) writes:
>I cured the problem with a cast:
>   ((long)(p1 - p->buf) + p->fpos) + 101

The compiler should have done essentially this for you in the first place.
The difference of two pointers within the same aggregate object is some
signed integral type; when that is added to a (long), it should have been
converted to (long) before the addition.