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From: Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups: comp.arch
Subject: Re: Computer architects leaving Intel...
Date: Wed, 11 Sep 2024 09:29:04 -0700
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Josh Vanderhoof <x@y.z> writes:

[how to write a portable, UB-free check if mempcy() intervals overlap]

> It is legal to test for equality between pointers to different objects

Right.  This observation is the key insight.

> so you could test for overlap by testing against every element in the
> array.

For a complete test, compare the address of every element in both
arrays.  For example:

   #include <stddef.h>

   _Bool
   memcpy_intervals_overlap( void *const vd, void *const vs, size_t n ){
     char    *d = vd,  *s = vs;
     size_t   k = 0;

       while(  k < n  &&  d != vs  &&  s != vd  )  k++,  d++,  s++;

       return  k < n;
   }