Date: Thu, 6 Jul 2017 14:13:26 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: Documentation of memcpy and undefined behavior in memset On Thu, Jul 06, 2017 at 08:38:29PM +0300, Alexander Monakov wrote: > On Thu, 6 Jul 2017, Rich Felker wrote: > > > 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. > > My view is that since in n=0 case no memory access inside of memcpy > takes place, the compiler may not deduce that the pointed-to object is > ok for speculative reads. Indeed, I think that's a valid interpretation, but not the only one; the problem here is that the specification is ambiguous, and I suspect nobody wants to fix the ambiguity because they know they're going to have an argument over what it was intended to mean... Rich
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