From: Jason Merrill <jason@redhat.com>
To: Jonathan Wakely <jwakely.gcc@gmail.com>, Andrew Haley <aph@redhat.com>
Cc: Andy Webber <andy@aligature.com>, gcc-help <gcc-help@gcc.gnu.org>,
Richard Biener <richard.guenther@gmail.com>
Subject: Re: is portable aliasing possible in C++?
Date: Fri, 05 Sep 2014 14:19:00 -0000 [thread overview]
Message-ID: <5409C666.4050607@redhat.com> (raw)
In-Reply-To: <CAH6eHdQxUNL0EbKJpT+qWfq_0py4eGQjqSKG99hjcWn3CBgOTg@mail.gmail.com>
On 09/04/2014 07:11 PM, Jonathan Wakely wrote:
> Placement new might work with GCC in practice as long as the buffer is
> correctly aligned and the type being constructed does not have
> non-trivial initialization. However, my reading of the standard is
> that after the placement new, if the object's members are not
> initialized then they have indeterminate values (not the values that
> were at those memory addresses already, even though that's likely to
> be what happens in practice).
I think that's a defect in the (non-normative) note in 5.3.4/17, which
is assuming that this follows from the rule in 8.5/12. But I don't
think it does, because in this case the storage has been initialized and
therefore is no longer indeterminate.
So I think the placement new form is OK.
Jason
next prev parent reply other threads:[~2014-09-05 14:19 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <A76FB9DDEDFA994BAF6B77704A4AF465BC2464@xchmbbal502.ds.susq.com>
2014-09-04 16:11 ` Andy Webber
2014-09-04 16:51 ` Andrew Haley
2014-09-04 17:18 ` Andy Webber
2014-09-04 17:23 ` Andrew Haley
2014-09-04 17:44 ` Andy Webber
2014-09-04 17:47 ` Andy Webber
2014-09-04 17:48 ` Andrew Haley
2014-09-04 23:11 ` Jonathan Wakely
2014-09-05 7:16 ` Andrew Haley
2014-09-05 14:19 ` Jason Merrill [this message]
2014-09-08 9:33 ` Richard Biener
2014-09-10 14:31 ` Jason Merrill
2014-09-09 23:13 haynberg
2014-09-10 8:17 ` Andrew Haley
2014-09-10 23:03 haynberg
2014-09-11 8:11 ` Andrew Haley
2014-09-11 23:25 ` haynberg
2014-09-12 8:32 ` Andrew Haley
2014-09-12 22:58 ` haynberg
2014-09-13 7:23 ` Andrew Haley
2014-09-13 11:45 ` Oleg Endo
2014-09-15 2:37 ` Hei Chan
2014-09-15 8:35 ` Andrew Haley
2014-09-15 11:07 ` Hei Chan
2014-09-15 11:21 ` Andrew Haley
2014-09-15 11:29 ` Hei Chan
2014-09-15 11:32 ` Andrew Haley
2014-09-15 11:57 ` Hei Chan
2014-09-15 13:21 ` Andrew Haley
2014-09-15 13:31 ` Hei Chan
2014-09-15 14:11 ` Andrew Haley
2014-09-15 11:27 ` Jonathan Wakely
2014-09-15 12:09 ` Paul Smith
2014-11-02 23:55 ` Hei Chan
2014-11-03 9:34 ` Andrew Haley
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=5409C666.4050607@redhat.com \
--to=jason@redhat.com \
--cc=andy@aligature.com \
--cc=aph@redhat.com \
--cc=gcc-help@gcc.gnu.org \
--cc=jwakely.gcc@gmail.com \
--cc=richard.guenther@gmail.com \
/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).