From: Gabriel Dos Reis <gdr@integrable-solutions.net>
To: Dale Johannesen <dalej@apple.com>
Cc: Andrew Haley <aph@redhat.com>,
"D. Hugh Redelmeier" <hugh@mimosa.com>,
gcc@gcc.gnu.org, Nathan Sidwell <nathan@codesourcery.com>,
Mike Stump <mrs@apple.com>
Subject: Re: volatile semantics
Date: Sat, 16 Jul 2005 21:17:00 -0000 [thread overview]
Message-ID: <m34qauv4d6.fsf@uniton.integrable-solutions.net> (raw)
In-Reply-To: <a315399723d359b46360b94cbdcb1af4@apple.com>
Dale Johannesen <dalej@apple.com> writes:
| > the type of an object
| > changes depending on how it is accessed.
|
| this also makes nonsense of gcc's implementation of type-based aliasing
| rules.
|
| *((int *)&x) = 3
No. That one is specifically covered by the C and C++ standards
(although they use different terminologies). C uses the notion of
*effective type* to formulate the rule.
[#6] The effective type of an object for an access to its
stored value is the declared type of the object, if any.72)
If a value is stored into an object having no declared type
through an lvalue having a type that is not a character
type, then the type of the lvalue becomes the effective type
of the object for that access and for subsequent accesses
that do not modify the stored value. If a value is copied
into an object having no declared type using memcpy or
memmove, or is copied as an array of character type, then
the effective type of the modified object for that access
and for subsequent accesses that do not modify the value is
the effective type of the object from which the value is
copied, if it has one. For all other accesses to an object
having no declared type, the effective type of the object is
simply the type of the lvalue used for the access.
-- Gaby
next prev parent reply other threads:[~2005-07-16 21:17 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
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 [this message]
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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