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From: c2a192@ugrad.cs.ubc.ca (Kazimir Kylheku)
Subject: Re: ANSI C and POSIX (was Re: C/C++ knocks the crap out of Ada)
Date: 1996/04/09
Message-ID: <4kf8k1INN68b@keats.ugrad.cs.ubc.ca>#1/1
X-Deja-AN: 146688344
references: <JSA.96Feb16135027@organon.com> <dewar.829051685@schonberg>
 <829066525snz@genesis.demon.co.uk> <dewar.829096975@schonberg>
organization: Computer Science, University of B.C., Vancouver, B.C., Canada
newsgroups: comp.lang.ada,comp.lang.c,comp.lang.c++,comp.edu
Date: 1996-04-09T00:00:00+00:00
List-Id: <comp.lang.ada>

In article <dewar.829096975@schonberg>, Robert Dewar <dewar@cs.nyu.edu> wrote:
 >Linux simply checks that the end of the buffer is in the memory area,
 >which is not the check you would like to see. That's what I was talking
 >about when I noted that this kind of uncertainty would not occur in
 >a language with a reasonably complete type model.

Precisely. The kernel defends itself against making a faulty dereference that
would trigger an exception, but will happily corrupt your valid data, unless
stated buffer range sticks over into an unmapped page.

 >What exactly *is* the wording of the POSIX standard here (Lawrence, you
 >must have it at hand, please quote it exactly). The interesting thing
 >is to determine whether this definition says enough to make *any* use
 >of read defined without appealing to "unwritten rules". I would guess
 >not!

Unwritten rules, or paranoia. Take your pick! (Door #2 for me, please)

The standard is basically very good at telling you what the functions do.

BTW, I checked the Ada POSIX standard too, but that reads like a VCR manual
from 1984.  ;)  heh
--