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From: sakkinen@jyu.fi (Markku Sakkinen)
Subject: Re: Zero-length structures and pointer comparisons
Message-ID: <1992Nov11.094404.7382@jyu.fi>
Organization: University of Jyvaskyla, Finland
References: <1992Oct30.003946.10484@microsoft.com> <1992Nov4.080805.13496@jyu.fi> <1992Nov10.185247.14128@sophists.com>
Date: Wed, 11 Nov 1992 09:44:04 GMT
Lines: 39

In article <1992Nov10.185247.14128@sophists.com> lewis@sophists.com (Lewis G. Pringle) writes:
>In article <1992Nov4.080805.13496@jyu.fi> sakkinen@jyu.fi (Markku Sakkinen) writes:
>...
>>I would first like to return to a much more important, related problem,
>>which somebody brought up here rather recently.
>> ...

I am still waiting for an answer to that question.
Nobody got a clue?

>I'd like to ask a related question.
>
>Given code like:
>
>char* start = new char [10];
>char* end   = start+10;
>char* p     = start;
> ...
>p = start;
>p--;
>assert (! ((p >= start) && (p <= end)));	// ???????
>
>Is the last assertion portable? ARM/ANSI-C References?

Certainly not portable.  The ARM (o. 72 - 73) says that 'p--' above
is undefined;  I would suppose that an implementation is allowed
even to abort the programme at that point.  Or, 'p > start' and
'p < start' might both yield true, and 'p >= start' and 'p <= start'
both false.

----------------------------------------------------------------------
Markku Sakkinen (sakkinen@jytko.jyu.fi)
       SAKKINEN@FINJYU.bitnet (alternative network address)
Department of Computer Science and Information Systems
University of Jyvaskyla (a's with umlauts)
PL 35
SF-40351 Jyvaskyla (umlauts again)
Finland
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