Path: ...!3.eu.feeder.erje.net!feeder.erje.net!news.in-chemnitz.de!news.swapon.de!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Michael S <already5chosen@yahoo.com>
Newsgroups: comp.arch
Subject: Re: Computer architects leaving Intel...
Date: Tue, 3 Sep 2024 19:09:28 +0300
Organization: A noiseless patient Spider
Lines: 57
Message-ID: <20240903190928.00002f92@yahoo.com>
References: <2024Aug30.161204@mips.complang.tuwien.ac.at>
	<memo.20240830164247.19028y@jgd.cix.co.uk>
	<vasruo$id3b$1@dont-email.me>
	<2024Aug30.195831@mips.complang.tuwien.ac.at>
	<vat5ap$jthk$2@dont-email.me>
	<vaunhb$vckc$1@dont-email.me>
	<vautmu$vr5r$1@dont-email.me>
	<2024Aug31.170347@mips.complang.tuwien.ac.at>
	<vavpnh$13tj0$2@dont-email.me>
	<vb2hir$1ju7q$1@dont-email.me>
	<8lcadjhnlcj5se1hrmo232viiccjk5alu4@4ax.com>
	<vb3k0m$1rth7$1@dont-email.me>
	<17d615c6a9e70e9fabe1721c55cfa176@www.novabbs.org>
	<86v7zep35n.fsf@linuxsc.com>
	<20240902180903.000035ee@yahoo.com>
	<vb7ank$3d0c5$1@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Injection-Date: Tue, 03 Sep 2024 18:08:45 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="6e614ad2247dbe6491c5f283904f9720";
	logging-data="3524382"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1/mJHRymJ9gsoO0fceZSbLcPJmWekb1srg="
Cancel-Lock: sha1:myB6lGxyZNnyJKNOAf6/XwAH6zg=
X-Newsreader: Claws Mail 3.19.1 (GTK+ 2.24.33; x86_64-w64-mingw32)
Bytes: 3659

On Tue, 3 Sep 2024 17:41:40 +0200
Terje Mathisen <terje.mathisen@tmsw.no> wrote:

> Michael S wrote:
> > On Mon, 02 Sep 2024 06:59:32 -0700
> > Tim Rentsch <tr.17687@z991.linuxsc.com> wrote:
> >   
> >> mitchalsup@aol.com (MitchAlsup1) writes:
> >>  
> >>> On Mon, 2 Sep 2024 5:55:34 +0000, Thomas Koenig wrote:
> >>>     
> >>>> George Neuner <gneuner2@comcast.net> schrieb:
> >>>>     
> >>>>> I'm not going to argue about whether UB in code is wrong.  The
> >>>>> question I have concerns what to do with something that
> >>>>> explicitly is mentioned as UB in some standard N, but was not
> >>>>> addressed in previous standards.
> >>>>>
> >>>>> Was it always UB?  Or should it be considered ID until it became
> >>>>> UB?  
> >>>>
> >>>> Can you give an exapmple?  
> >>>
> >>> Memcopy() with overlapping pointers.  
> >>
> >> Calling memcpy() between objects that overlap has always been
> >> explicitly and specifically undefined behavior, going back to
> >> the original ANSI C standard.  
> > 
> > 3 years ago Terje Mathisen wrote that many years ago he read that
> > behaviour of memcpy() with overlappped src/dst was defined.
> > https://groups.google.com/g/comp.arch/c/rSk8c7Urd_Y/m/ZWEG5V1KAQAJ
> > Mitch Alsup answered "That was true in 1983".
> > So, two people of different age living in different parts of the
> > world are telling the same story. May be, there exist old popular
> > book that said that it was defined?
> >   
> 
> It probably wasn't written in the official C standard, which I
> couldn't have afforded to buy/read, but in a compiler runtime doc?
> 
> Specifying that it would always copy from beginning to end of the
> source buffer, in increasing address order meant that it was
> guaranteed safe when used to compact buffers.
>

What is "compact buffers" ?

> Code that depended on this was fine for decades, until the first 
> library/compiler implementation discovered that in some circumstances
> it could be faster to go in reverse order.
> 
> Terje
> 
>