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From: Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups: comp.std.c
Subject: Re: May a string span multiple, independent objects?
Date: Thu, 08 Aug 2024 08:51:26 -0700
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Hans-Bernhard Bröker <HBBroeker@gmail.com> writes:

> Comparing pointers pointing at distinct objects is already invalid
> (for some interpretation of "invalid"), [...].

Using relational operators (<, <=, >, >=) to compare pointers to
distinct objects has defined behavor only if the pointed-to objects
are sub-objects of the same containing object.

Equality operators (==, !=) may be used, with defined behavior,
to compare pointers to any objects, regardless of whether the
pointed-to objects belong to an enclosing containing object.

> Yes, that means the implementation of a function like memmove()
> cannot be fully portable C.

The function memmove() can be defined in fully portable C.  It's
just more convenient to write it in a way that takes advantage of
implementation internals.