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From: James Kuyper <jameskuyper@alumni.caltech.edu>
Newsgroups: comp.std.c
Subject: Re: May a string span multiple, independent objects?
Date: Wed, 3 Jul 2024 12:11:25 -0400
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On 7/3/24 11:23, Hans-Bernhard Bröker wrote:
> Am 03.07.2024 um 16:31 schrieb Vincent Lefevre:
>> ISO C17 (and C23 draft) 7.1.1 defines a string as follows: "A string
>> is a contiguous sequence of characters terminated by and including
>> the first null character."
>>
>> But may a string span multiple, independent objects that happens
>> to be contiguous in memory?
>>
>> For instance, is the following program valid and what does the ISO C
>> standard say about that?
> 
> Comparing pointers pointing at distinct objects is already invalid (for 
> some interpretation of "invalid")

Comparison of valid pointers that point at distinct objects has
well-defined behavior. Such operations would be pretty useless if that
weren't the case, since they only compare the locations of those objects
- if they were allowed only for objects that are  not distinct, the
locations would necessarily be the same, so, ==, <= and >= would always
return true, and !=, <, and > would always return false.

Furthermore, comparison for equality (as opposed to comparison for
relative order) is permitted even for objects that aren't sub-objects of
the same larger object. The problems with such code involves
incrementing and dereferencing such pointers, not comparing them.