Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!uunet!munnari.oz.au!csc!bdm659
From: bdm659@csc.anu.oz
Newsgroups: comp.std.c
Subject: Re: null pointers of type JOKE* can't be dereferenced
Message-ID: <891.254d8d35@csc.anu.oz>
Date: 31 Oct 89 12:16:50 GMT
References: <11380@smoke.BRL.MIL> <8952@goofy.megatest.UUCP> <872.254895b5@csc.anu.oz> <11432@smoke.BRL.MIL> <876.2549cbb7@csc.anu.oz> <879.254a0ba0@csc.anu.oz> <11441@smoke.BRL.MIL>
Organization: Computer Services, Australian National University
Lines: 30

In article <11441@smoke.BRL.MIL>, gwyn@smoke.BRL.MIL (Doug Gwyn) writes:
>
> There is another point worth making here.  The Standard must be
> subjected to more than mere "linguistic analysis" in order to
> understand what it is saying; there is a gestalt that must be
> acquired, and it goes beyond the simple expansion of words in
> terms of their definitions, just as concepts in general embody
> much more than is found in their literal definitions.

  That's clearly true, though one valid measure of the success of the standard
is how readily an "average technically competent person" can acquire that
gestalt by studying the document.
  It's also true that it would be unfair to expect a technical document of this
complexity to have the rigor and internal consistency that we might expect of
a mathematical proof.  That doesn't mean that inconsistencies shouldn't be
pointed out (I intend to--this isn't sacred scripture); it means that they need
not be taken too seriously unless they are genuinely likely to mislead someone.

I'm told that the sentence I quoted from 3.3.9 now reads

    "If two pointers to object or incomplete types compare equal, they both
    are null pointers, or both point to the same object, or both point one
    past the last element of the same array object.".

The previous version of the sentence was simply false.
[It used to be much worse, though.  I'm fairly sure that the draft of May 87
is literally satisfied by an implementation in which all pointers compare
equal always.]

Brendan McKay.   bdm@anucsd.oz  or   bdm@anucsd.oz.au