From: Mark Mitchell <mark@codesourcery.com>
To: Joe Buck <jbuck@synopsys.COM>, Daniel Berlin <dan@dberlin.org>
Cc: Neil Booth <neil@daikokuya.demon.co.uk>,
Paolo Carlini <pcarlini@unitus.it>,
"gcc@gcc.gnu.org" <gcc@gcc.gnu.org>
Subject: Re: g++ and aliasing bools
Date: Mon, 28 Jan 2002 15:59:00 -0000 [thread overview]
Message-ID: <11140000.1012259923@gandalf.codesourcery.com> (raw)
In-Reply-To: <200201281722.JAA08937@atrus.synopsys.com>
[ zero-sized based class example elided ]
>
> But the C aliasing rules completely ignore the question of size, so you're
> bringing up a red herring. The rules have *nothing* to do with whether we
> think that two objects have the same address! It doesn't even come up.
> For that reason, you don't have to waste any time thinking about class
> layout.
>
Joe's argument is a reduction from C++ to C; the claim is that (basically)
the C++ alias rules are the same as C and that certain C++ classes are
laid out like certain C structs and that there are no additional
"dangerous" operations and therefore correctness for C implies correctness
for C++.
The argument doesn't work in this case -- the proposed isomorphism from
C++ classes to C structs is not correct.
Joe's argument either needs to handle zero-sized classes in some other
way (arguing that they're not dangerous for some other reason), or it
needs to not apply to class hierarchives that involve zero-sized bases,
treating such things as not simple_enough.
--
Mark Mitchell mark@codesourcery.com
CodeSourcery, LLC http://www.codesourcery.com
next prev parent reply other threads:[~2002-01-28 23:20 UTC|newest]
Thread overview: 97+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-01-25 8:55 Robert Dewar
2002-01-25 9:21 ` Daniel Berlin
2002-01-25 10:00 ` Daniel Berlin
2002-01-25 10:54 ` Paolo Carlini
2002-01-25 11:37 ` Daniel Berlin
2002-01-25 11:45 ` David Edelsohn
2002-01-25 11:53 ` Joe Buck
2002-01-25 12:09 ` Mark Mitchell
2002-01-25 12:28 ` Paolo Carlini
2002-01-25 13:49 ` Mark Mitchell
2002-01-25 14:19 ` Joe Buck
2002-01-25 14:21 ` Mark Mitchell
2002-01-25 15:41 ` Neil Booth
2002-01-25 16:04 ` Joe Buck
2002-01-25 17:37 ` Paolo Carlini
2002-01-25 18:10 ` Daniel Berlin
2002-01-27 5:11 ` Mark Mitchell
2002-01-27 5:34 ` Daniel Berlin
2002-01-28 10:39 ` Joe Buck
2002-01-28 10:51 ` Joe Buck
2002-01-28 15:59 ` Mark Mitchell [this message]
2002-01-28 17:11 ` Daniel Berlin
2002-01-28 17:28 ` Joe Buck
2002-01-28 18:14 ` Daniel Berlin
2002-01-28 17:18 ` Joe Buck
2002-01-28 18:05 ` Mark Mitchell
2002-01-28 18:50 ` Joe Buck
2002-01-28 19:33 ` Mark Mitchell
2002-01-28 17:40 ` Daniel Berlin
2002-01-28 21:55 ` Daniel Berlin
2002-01-28 22:02 ` Alexandre Oliva
2002-01-28 22:12 ` Mark Mitchell
2002-01-25 13:07 ` Joe Buck
2002-01-25 15:43 ` Daniel Berlin
2002-01-25 16:03 ` Joe Buck
2002-01-25 15:13 ` Daniel Berlin
2002-01-25 12:10 ` Paolo Carlini
2002-01-25 13:16 ` Joe Buck
2002-01-25 15:23 ` Daniel Berlin
2002-01-25 12:05 ` Mark Mitchell
2002-01-25 22:14 ` Daniel Berlin
2002-01-26 3:46 ` Mark Mitchell
-- strict thread matches above, loose matches on Subject: below --
2002-01-25 14:49 mike stump
2002-01-25 12:23 Robert Dewar
2002-01-25 13:29 ` Joe Buck
2002-01-25 12:06 mike stump
2002-01-25 9:13 Robert Dewar
2002-01-25 8:35 Robert Dewar
2002-01-25 8:54 ` Daniel Berlin
2002-01-25 8:33 Richard Kenner
2002-01-25 8:32 Robert Dewar
2002-01-25 8:53 ` Daniel Berlin
2002-01-25 9:39 ` Joe Buck
2002-01-25 8:28 Robert Dewar
2002-01-25 8:49 ` Daniel Berlin
2002-01-25 7:51 Robert Dewar
2002-01-25 8:18 ` Daniel Berlin
2002-01-25 8:20 ` Daniel Berlin
2002-01-25 7:38 Robert Dewar
2002-01-25 8:11 ` Daniel Berlin
2002-01-25 14:09 ` Gabriel Dos Reis
2002-01-25 7:30 Richard Kenner
2002-01-25 7:33 ` Daniel Berlin
2002-01-25 15:43 ` Daniel Berlin
2002-01-25 7:30 Richard Kenner
2002-01-25 7:23 Richard Kenner
2002-01-25 7:24 ` Daniel Berlin
2002-01-25 7:05 Richard Kenner
2002-01-25 8:59 ` Paolo Carlini
2002-01-24 16:09 Richard Kenner
2002-01-24 15:30 Richard Kenner
2002-01-25 2:16 ` Gabriel Dos Reis
2002-01-25 3:04 ` Paolo Carlini
2002-01-25 4:17 ` Gabriel Dos Reis
2002-01-25 4:35 ` Paolo Carlini
2002-01-25 6:34 ` Daniel Berlin
2002-01-25 7:17 ` Daniel Berlin
2002-01-25 13:57 ` Gabriel Dos Reis
2002-01-25 14:47 ` Tim Hollebeek
2002-01-23 17:56 Dan Nicolaescu
2002-01-23 18:27 ` Daniel Berlin
2002-01-23 18:48 ` Dan Nicolaescu
2002-01-23 19:16 ` Daniel Berlin
2002-01-24 14:15 ` Mark Mitchell
2002-01-24 14:16 ` Daniel Berlin
2002-01-24 14:27 ` Mark Mitchell
2002-01-24 14:35 ` Daniel Berlin
2002-01-24 15:06 ` Mark Mitchell
2002-01-24 15:08 ` Paolo Carlini
2002-01-24 15:18 ` Dan Nicolaescu
2002-01-24 15:36 ` Mark Mitchell
2002-01-25 2:25 ` Daniel Berlin
2002-01-25 15:48 ` Dan Nicolaescu
2002-01-25 20:22 ` Joe Buck
2002-01-25 23:59 ` Daniel Berlin
2002-01-27 17:04 ` Dan Nicolaescu
2002-01-27 17:59 ` Paolo Carlini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=11140000.1012259923@gandalf.codesourcery.com \
--to=mark@codesourcery.com \
--cc=dan@dberlin.org \
--cc=gcc@gcc.gnu.org \
--cc=jbuck@synopsys.COM \
--cc=neil@daikokuya.demon.co.uk \
--cc=pcarlini@unitus.it \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).