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Date: Thu, 6 Jul 2017 13:22:18 -0400
From: Rich Felker <>
Subject: Re: Documentation of memcpy and undefined behavior in memset

On Thu, Jul 06, 2017 at 08:17:32PM +0300, Alexander Monakov wrote:
> On Thu, 6 Jul 2017, Rich Felker wrote:
> > If p points to one past the end of an object that ends on a page
> > boundary, this transformation could introduce a crash.
> The object beginning at p (i.e. the array beginning just after the
> array which p was derived from) could be volatile, making that an
> invalid transformation. Nothing gives the compiler a guarantee
> that that area is non-volatile.

I'm doubtful of this. Certainly passing a pointer to memcpy with a
nonzero n is a guarantee that the pointed-to object is non-volatile.
The n=0 case is less clear though.


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