Path: csiph.com!eeepc.pasdenom.info!news.pasdenom.info!news.dougwise.org!gegeweb.org!eternal-september.org!feeder.eternal-september.org!.POSTED!not-for-mail
From: Alexander Terekhov <terekhov@web.de>
Newsgroups: comp.programming.threads
Subject: Re: forcing the compiler to reload from memory with c++0x
Date: Wed, 02 Feb 2011 14:45:04 +0100
Organization: A noiseless patient Spider
Lines: 38
Message-ID: <4D495FE0.ED8A251E@web.de>
References: <4d3cee42$0$1209$426a74cc@news.free.fr> <1d21ad0a-db55-460e-aeb6-66f6d19369ea@i13g2000yqe.googlegroups.com> <4d3e2e3f$0$21517$426a34cc@news.free.fr> <4D40A4C7.16E6F9AE@web.de> <69d82db7-34be-4de7-86c4-2f39cc1e6df3@m13g2000yqb.googlegroups.com> <4d4221e9$0$17247$426a74cc@news.free.fr> <947b33d5-2509-4f0c-9256-a7c3de35578e@24g2000yqa.googlegroups.com> <87mxmlxxry.fsf@justsoftwaresolutions.co.uk> <ihv8t6$bmr$1@news.eternal-september.org> <87oc6yxdcw.fsf@justsoftwaresolutions.co.uk> <ii745u$5q3$1@news.eternal-september.org> <87sjw8w4b5.fsf@justsoftwaresolutions.co.uk> <4D480800.1C5132D7@web.de> <87k4hjx3ph.fsf@justsoftwaresolutions.co.uk> <4D482797.CBE41A86@web.de> <90c4d6f1-c539-4fdc-9b20-2cc6bc92dbe4@z20g2000yqe.googlegroups.com> <4D493C5C.83CA38C@web.de> <e065a7dd-2251-4568-b914-e3e5dc7269aa@x1g2000yqb.googlegroups.com>
Reply-To: terekhov@web.de
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Injection-Info: mx01.eternal-september.org; posting-host="3e4Fotn8NP3CUoQPJwS9VQ"; logging-data="1479"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1+ZSZoXD2Xnux3rJHL2d/7k3SldmYvD/TM="
X-Mailer: Mozilla 4.77 [en] (Windows NT 5.0; U)
X-Accept-Language: en
Cancel-Lock: sha1:OarFZBn1blBV0Mnc1H4CQDgo92k=
Xref: csiph.com comp.programming.threads:1789


Dmitriy Vyukov wrote:
[...]
> Alexander, you are inconsistent here.
> Why can't printf() output go to nowhere on its own in the first place?
> Abstract output is basically the same as abstract memory accesses on
> abstract machine, no? And what is that abstract "standard output"
> device or file? If we go down to that formal hair-splitting level,
> then I believe we won't conclude anything useful. For example, is
> there dynamic memory? Well, I'm not sure. Is zero bytes of dynamic
> memory still dynamic memory? I guess it's nothing.
> If you want, there is always an implementation. And it's possible to
> loosely define such group of implementations as "sane industrial
> implementations". And in that context volatile access indeed means the
> most natural memory access instruction in generated code (MOV, LD or
> whatever). And that is observable. And that is what Anthony meant, I
> think.

Stop abstracting into absurdity. "MOV, LD or whatever" are not
externally observable in the case of

int main() {
  volatile int i;
  // volatile write = has no observable effect
  i = 1;
  // volatile read = has no observable effect
  int n = i;
}

because the above program is the same as

int main() {
}

for any reasonable observer of the outcome.

regards,
alexander.