From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,5697899e4423465c X-Google-Attributes: gid103376,public From: dewarr@my-dejanews.com Subject: Re: null pointer representation (was: Boolean Representation) Date: 1998/09/28 Message-ID: <6uo7p6$dk4$1@nnrp1.dejanews.com>#1/1 X-Deja-AN: 395614568 References: <6umkbn$pv5$1@nnrp1.dejanews.com> X-Http-Proxy: 1.0 x1.dejanews.com:80 (Squid/1.1.22) for client 209.73.133.253 Organization: Deja News - The Leader in Internet Discussion X-Article-Creation-Date: Mon Sep 28 14:51:18 1998 GMT Newsgroups: comp.lang.ada X-Http-User-Agent: Mozilla/2.02 (OS/2; I) Date: 1998-09-28T00:00:00+00:00 List-Id: In article , Keith Thompson wrote: > dewarr@my-dejanews.com writes: > [...] > > Certainly though, you are right, Null_Address can be assumed to be all > > zero bits in practice, but not Null. > > Why is it safe to assume that Null_Address is all zero bits? > I'd normally expect it to have the same representation as a null > pointer, though of course that's not guaranteed either. > > (In any case, since Null_Address is conveniently declared in System, > there's no need to assume anything about how it's represented.) What is and is not safe to assume cannot be derived only from ISO standards! For all sorts of reasons, it is safe to assume that Null_Address is all zero bits. If you think this is wrong, cough up a counter example :-) Still, of course it is better never to have to depend on this assumption if you can avoid it (the same comment applies exactly equivalently to C code) -----== Posted via Deja News, The Leader in Internet Discussion ==----- http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum