From: Martin Krischik <krischik@users.sourceforge.net>
Subject: Re: volatile vs aliased
Date: Fri, 07 Oct 2005 08:36:32 +0200
Date: 2005-10-07T08:36:32+02:00 [thread overview]
Message-ID: <2245220.uuDKIncv1a@linux1.krischik.com> (raw)
In-Reply-To: 4fe1f.147855$dP1.505453@newsc.telia.net
Bjï¿œrn Persson wrote:
> Rolf wrote:
>> Do we have a difference to C/C++ increment operator here? consider
>>
>> pragma Volatile (x);
>> x := x + 1; -- (1)
>> vs.
>> x++; -- (2)
>>
>> In the Ada case (1) we are forced to have "read from memory",
>> "increment" and "write to memory" instructions, whereas in C/C++ (2)
>> you can get a single "increment memory" instruction (presuming the
>> mentioned assembler instructions exist on a given processor)
>
> Are there really memory chips with built-in arithmetic circuitry, so
> that the processor can send an "add one" instruction to the memory and
> have the variable incremented without reading it first? At least I've
> never heard of that. As far as I know, adding and subtracting is the
> processor's job.
>
> And why would you use pragma Volatile on a variable stored in the
> memory, anyway? As Ludovic described it, it would only be useful on
> variables mapped to special hardware devices. I don't think you would
> want to store a counter there.
Or you have a multi tasking application with C interface.
Martin
--
mailto://krischik@users.sourceforge.net
Ada programming at: http://ada.krischik.com
next prev parent reply other threads:[~2005-10-07 6:36 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-10-05 15:22 volatile vs aliased REH
2005-10-05 18:22 ` Ludovic Brenta
2005-10-05 18:39 ` REH
2005-10-05 19:46 ` Ludovic Brenta
2005-10-05 20:02 ` REH
2005-10-05 20:11 ` Ludovic Brenta
2005-10-05 20:20 ` REH
2005-10-06 5:21 ` Ludovic Brenta
2005-10-05 20:55 ` Simon Wright
2005-10-06 18:32 ` Jeffrey R. Carter
2005-10-05 23:38 ` Randy Brukardt
2005-10-06 0:02 ` tmoran
2005-10-06 13:40 ` REH
2005-10-06 23:52 ` Randy Brukardt
2005-10-06 18:40 ` Jeffrey R. Carter
2005-10-06 19:37 ` Robert A Duff
2005-10-06 23:56 ` Randy Brukardt
2005-10-06 19:08 ` REH
2005-10-06 19:21 ` Ed Falis
2005-10-06 19:37 ` REH
2005-10-06 19:46 ` Robert A Duff
2005-10-06 8:05 ` Martin Krischik
2005-10-06 8:52 ` Dmitry A. Kazakov
2005-10-06 11:36 ` Rolf
2005-10-06 18:43 ` Björn Persson
2005-10-06 19:03 ` Niklas Holsti
2005-10-07 6:36 ` Martin Krischik [this message]
2005-10-07 6:33 ` Martin Krischik
2005-10-07 15:56 ` Adrian Knoth
2005-10-07 18:48 ` Martin Krischik
2005-10-07 22:44 ` REH
2005-10-08 6:10 ` Simon Wright
2005-10-17 2:16 ` Dave Thompson
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