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=-1.9 required=5.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.4
X-Google-Thread: 103376,c9d5fc258548b22a
X-Google-NewGroupId: yes
X-Google-Attributes: gida07f3367d7,domainid0,public,usenet
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news1.google.com!postnews.google.com!4g2000yqo.googlegroups.com!not-for-mail
From: Ludovic Brenta <ludovic@ludovic-brenta.org>
Newsgroups: comp.lang.ada
Subject: Re: How do I write directly to a memory address?
Date: Fri, 4 Feb 2011 01:21:20 -0800 (PST)
Organization: http://groups.google.com
Message-ID: <3abe5305-bf28-4bec-9f55-b382d7140c17@4g2000yqo.googlegroups.com>
References: 
 <67063a5b-f588-45ea-bf22-ca4ba0196ee6@l11g2000yqb.googlegroups.com>
 <31c357bd-c8dc-4583-a454-86d9c579e5f4@m13g2000yqb.googlegroups.com>
 <iiest7$kq8$1@tornado.tornevall.net>
NNTP-Posting-Host: 153.98.68.197
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
X-Trace: posting.google.com 1296811280 29046 127.0.0.1 (4 Feb 2011 09:21:20
 GMT)
X-Complaints-To: groups-abuse@google.com
NNTP-Posting-Date: Fri, 4 Feb 2011 09:21:20 +0000 (UTC)
Complaints-To: groups-abuse@google.com
Injection-Info: 4g2000yqo.googlegroups.com; posting-host=153.98.68.197;
 posting-account=pcLQNgkAAAD9TrXkhkIgiY6-MDtJjIlC
User-Agent: G2/1.0
X-HTTP-UserAgent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.0.6)
 Gecko/2009012111 Red Hat/3.0.6-1.el5 Firefox/3.0.6,gzip(gfe)
Xref: g2news1.google.com comp.lang.ada:16861
Date: 2011-02-04T01:21:20-08:00
List-Id: <comp.lang.ada>

Jeffrey Carter wrote:
>> *Every* time I look at C code, I see a bug.
>> I think this is a bug; it should read "message++" since you want to
>> increment the pointer, not the pointed-to character.
>
> As others have explained, this is not an error, though the unused dereference is
> wasted effort. However, if message does not contain zero, this will happily read
> memory outside of message, and if the first zero encountered follows enough
> bytes, it will happily write memory outside of vidmem.

OK, so my hunch was wrong; there was not one but two bugs in that
line.

Funny to see that my quickly-written, untested Ada code cannot
possibly have these bugs. Proper arrays prevent reading the
terminating null character since there isn't one; the modular types
for the indexes prevent writing outside the video buffer.  Once more,
praise the Lady :)

--
Ludovic Brenta.