From: Gabriel Dos Reis <gdr@integrable-solutions.net>
To: Geoff Keating <geoffk@geoffk.org>
Cc: Ian Lance Taylor <ian@airs.com>, Andrew Haley <aph@redhat.com>,
"D. Hugh Redelmeier" <hugh@mimosa.com>,
gcc@gcc.gnu.org, Nathan Sidwell <nathan@codesourcery.com>,
Dale Johannesen <dalej@apple.com>, Mike Stump <mrs@apple.com>
Subject: Re: volatile semantics
Date: Sat, 23 Jul 2005 02:59:00 -0000 [thread overview]
Message-ID: <m3fyu6rzyo.fsf@uniton.integrable-solutions.net> (raw)
In-Reply-To: <3D9CE704-A395-4203-94B1-222158DDFAA4@geoffk.org>
Geoff Keating <geoffk@geoffk.org> writes:
| On 22/07/2005, at 4:33 PM, Ian Lance Taylor wrote:
|
| > Geoffrey Keating <geoffk@geoffk.org> writes:
| >
| >> Although I can see that this is how you might think about the
| >> semantics of 'const' and 'volatile', I don't think they're an exact
| >> match for the model in the standard. In fact, I think you could
| >> exchange the words 'const' and 'volatile' in the above and they would
| >> be equally accurate.
| >>
| >
| > Sure, and I think my ultimate point would still be accurate: gcc
| > should handle the access using the qualification of the pointer, not
| > of the underlying object. The rest of the argument is just
| > motivation.
|
| By "equally accurate", I also meant "equally inaccurate".
|
| You've successfully argued that 'const' and 'volatile' are the same
| in lots of ways; but 'const' and 'volatile' do differ. In order to
| be successful in this argument, you need to argue that the
| differences don't matter.
|
| And, unfortunately, the differences *do* matter. The standard does
| not say "any expression referring to a volatile-qualified type must
| be evaluated strictly according to the rules of the abstract
| machine". What it says is that "An object that has volatile
| qualified type may be modified in ways unknown to the implementation"
| and then lists some of the consequences of an object being modifiable
| in that way. So there are no "semantics of the access"; the
| semantics attach to the object.
I disagree with statement. There is a "semantics of access". It is
implementation-defined.
| This is part of what I meant by saying that your model isn't a match
| for the model in the standard. Your model had semantics attached to
| the access.
On the contrary, I find his moel most faithful than the interpretation
you offer. The standard describes things like side effect and such in
terms of *access*.
-- Gaby
next prev parent reply other threads:[~2005-07-23 2:59 UTC|newest]
Thread overview: 118+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-05-03 8:41 Mike Stump
2005-05-03 8:52 ` Paolo Bonzini
2005-05-03 9:53 ` Giovanni Bajo
2005-05-03 14:31 ` Dave Korn
2005-05-03 14:41 ` Nathan Sidwell
2005-05-03 17:04 ` Dale Johannesen
2005-05-03 18:03 ` Nathan Sidwell
2005-05-03 18:32 ` Paul Koning
2005-05-03 18:37 ` Dale Johannesen
2005-05-11 23:01 ` Geoffrey Keating
2005-05-12 14:46 ` Paul Koning
2005-05-03 18:35 ` Dale Johannesen
2005-05-03 18:54 ` Nathan Sidwell
2005-05-03 19:25 ` Dale Johannesen
2005-05-04 8:18 ` Nathan Sidwell
2005-05-04 10:23 ` Andrew Haley
2005-05-04 11:30 ` Gabriel Dos Reis
2005-05-04 17:59 ` Dale Johannesen
2005-05-04 18:01 ` Paul Koning
2005-05-04 19:49 ` Nathan Sidwell
2005-07-16 16:51 ` D. Hugh Redelmeier
2005-07-16 16:56 ` Daniel Berlin
2005-07-16 17:26 ` Nathan Sidwell
2005-07-16 17:32 ` Daniel Berlin
2005-07-16 18:35 ` Nathan Sidwell
2005-07-16 20:35 ` Daniel Berlin
2005-07-16 21:29 ` Gabriel Dos Reis
2005-07-16 21:41 ` Daniel Berlin
2005-07-16 21:59 ` Gabriel Dos Reis
2005-07-16 21:07 ` Gabriel Dos Reis
2005-07-16 19:20 ` D. Hugh Redelmeier
2005-07-16 21:10 ` Gabriel Dos Reis
2005-07-16 20:52 ` Gabriel Dos Reis
2005-07-16 21:07 ` Daniel Berlin
2005-07-16 21:24 ` Gabriel Dos Reis
2005-07-16 21:30 ` Daniel Berlin
2005-07-16 22:19 ` Gabriel Dos Reis
2005-07-16 21:36 ` Daniel Berlin
2005-07-16 22:06 ` Gabriel Dos Reis
2005-07-16 22:17 ` Daniel Berlin
2005-07-16 22:25 ` Gabriel Dos Reis
2005-07-19 7:27 ` Kai Henningsen
2005-07-19 9:25 ` Gabriel Dos Reis
2005-07-16 22:34 ` D. Hugh Redelmeier
2005-07-16 22:57 ` Gabriel Dos Reis
2005-07-17 1:37 ` D. Hugh Redelmeier
2005-07-17 2:24 ` Gabriel Dos Reis
2005-07-17 2:36 ` Daniel Berlin
2005-07-17 3:08 ` Gabriel Dos Reis
2005-07-17 4:32 ` Michael Veksler
2005-07-17 5:19 ` Michael Veksler
2005-07-17 5:31 ` Gabriel Dos Reis
2005-07-17 7:33 ` Michael Veksler
2005-07-17 14:33 ` Daniel Berlin
2005-07-17 15:30 ` Michael Veksler
2005-07-17 7:53 ` Andrew Pinski
2005-07-17 11:41 ` Gabriel Dos Reis
2005-07-17 7:40 ` D. Hugh Redelmeier
2005-07-17 11:50 ` Gabriel Dos Reis
2005-07-18 19:30 ` Mike Stump
2005-07-18 20:05 ` Gabriel Dos Reis
2005-07-17 15:45 ` Richard Henderson
2005-07-17 16:04 ` Nathan Sidwell
2005-07-17 16:18 ` Richard Henderson
2005-07-17 16:54 ` Gabriel Dos Reis
2005-07-17 16:06 ` Falk Hueffner
2005-07-17 16:18 ` Ian Lance Taylor
2005-07-17 16:44 ` Richard Henderson
2005-07-17 12:49 ` Joseph S. Myers
2005-07-17 2:27 ` Daniel Berlin
2005-07-17 3:14 ` Gabriel Dos Reis
2005-07-17 3:27 ` Daniel Berlin
2005-07-17 20:34 ` Mark Mitchell
2005-07-17 4:38 ` D. Hugh Redelmeier
2005-07-17 5:27 ` Gabriel Dos Reis
2005-07-18 13:13 ` Gerald Pfeifer
2005-07-17 7:54 ` D. Hugh Redelmeier
2005-07-17 10:11 ` Andrew Haley
2005-07-17 12:03 ` Gabriel Dos Reis
2005-07-16 17:33 ` Andrew Haley
2005-07-16 17:53 ` Daniel Berlin
2005-07-17 8:25 ` Ian Lance Taylor
2005-07-22 23:20 ` Geoffrey Keating
2005-07-22 23:33 ` Ian Lance Taylor
2005-07-23 1:28 ` Geoff Keating
2005-07-23 2:59 ` Gabriel Dos Reis [this message]
2005-07-23 9:50 ` Geoff Keating
2005-07-23 6:03 ` Ian Lance Taylor
2005-07-23 16:03 ` Mike Stump
2005-07-16 19:05 ` Dale Johannesen
2005-07-16 21:17 ` Gabriel Dos Reis
2005-07-22 23:20 ` Geoffrey Keating
2005-07-25 23:08 ` Olivier Galibert
2005-05-06 0:45 ` Kai Henningsen
2005-05-06 1:42 ` Paul Koning
2005-05-06 2:04 ` Gabriel Dos Reis
2005-05-06 2:57 ` Dale Johannesen
2005-05-03 21:19 ` Thorsten Glaser
2005-05-06 5:06 Paul Schlie
2005-07-17 17:58 Paul Schlie
2005-07-18 1:29 Paul Schlie
2005-07-18 6:36 ` Gabriel Dos Reis
2005-07-18 11:20 ` Paul Schlie
2005-07-18 12:12 ` Paolo Bonzini
2005-07-18 12:17 ` Paul Schlie
2005-07-18 12:27 ` Gabriel Dos Reis
2005-07-18 13:27 ` Paul Schlie
2005-07-18 15:47 ` D. Hugh Redelmeier
2005-07-18 12:24 ` Gabriel Dos Reis
2005-07-18 12:11 ` Jonathan Wakely
2005-07-18 12:31 ` Paul Schlie
2005-07-19 17:56 Paul Schlie
2005-07-19 18:13 ` Gabriel Dos Reis
2005-07-19 18:32 ` Paul Schlie
2005-07-23 2:15 Paul Schlie
2005-07-23 9:50 ` Geoff Keating
2005-07-23 11:39 ` Paul Schlie
2005-07-23 11:44 ` Paul Schlie
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