public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "post+gcc at ralfj dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/32667] block copy with exact overlap is expanded as memcpy
Date: Sat, 28 Oct 2023 10:04:21 +0000 [thread overview]
Message-ID: <bug-32667-4-RPoQbCLNJP@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-32667-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=32667
post+gcc at ralfj dot de changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |post+gcc at ralfj dot de
--- Comment #23 from post+gcc at ralfj dot de ---
> Is glibc community ready to provide such guarantee?
This is indeed a key question here I think. Currently GCC makes assumptions
that *even the libc produced by the same project* does not document as stable
guarantees. That's rather dissonant. The GNU project should at least within
itself come to a proper conclusion on the question of whether memcpy should be
UB or not when both pointers are equal. Right now we have everyone pointing at
everyone else, and users are left in the rain with their valgrind errors.
Ideally of course the C standard would be updated to ensure that slowly but
steadily, the memcpy contract is updated to match reality. That will take a
while, but given that this issue was filed 16 years ago (!), there clearly
would have been enough time. (If someone does, please join forces with the
clang people that are interested in getting C updated:
https://reviews.llvm.org/D86993#4585590).
But GNU controls glibc so there's not really any excuse for not updating those
docs, I think? glibc making such a move would be a great step towards
convincing valgrind and the C committee that memcpy should have defined
behavior when both pointers are equal.
next prev parent reply other threads:[~2023-10-28 10:04 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-32667-4@http.gcc.gnu.org/bugzilla/>
2011-12-05 17:00 ` [Bug middle-end/32667] builtin operator= generates memcpy with overlapping memory regions lu_zero at gentoo dot org
2011-12-05 20:38 ` mans at mansr dot com
2011-12-06 8:46 ` [Bug middle-end/32667] block copy with exact overlap is expanded as memcpy rguenth at gcc dot gnu.org
2015-02-12 5:38 ` pinskia at gcc dot gnu.org
2015-02-12 9:00 ` rguenth at gcc dot gnu.org
2015-02-12 9:42 ` jakub at gcc dot gnu.org
2015-09-28 18:18 ` hugh at mimosa dot com
2021-06-09 18:50 ` public at timruffing dot de
2021-06-10 6:36 ` rguenther at suse dot de
2023-01-05 8:53 ` pinskia at gcc dot gnu.org
2023-01-05 9:19 ` nyh at math dot technion.ac.il
2023-01-06 18:48 ` lopresti at gmail dot com
2023-10-28 10:04 ` post+gcc at ralfj dot de [this message]
2023-11-21 15:57 ` bugdal at aerifal dot cx
2023-11-22 7:33 ` rguenther at suse dot de
2023-11-22 14:57 ` bugdal at aerifal dot cx
2023-11-22 15:06 ` jakub at gcc dot gnu.org
2023-11-22 19:07 ` bugdal at aerifal dot cx
2023-11-23 0:00 ` lopresti at gmail dot com
2023-11-23 7:44 ` post+gcc at ralfj dot de
2023-11-23 7:58 ` rguenth at gcc dot gnu.org
2023-11-23 8:03 ` fw at gcc dot gnu.org
2023-11-23 8:08 ` rguenther at suse dot de
2023-11-23 8:32 ` cvs-commit at gcc dot gnu.org
2023-11-23 8:39 ` jakub at gcc dot gnu.org
2023-11-23 13:54 ` bugdal at aerifal dot cx
2023-11-23 13:57 ` bugdal at aerifal dot cx
2023-11-23 14:41 ` public at timruffing dot de
2023-11-23 15:00 ` public at timruffing dot de
2023-11-23 15:01 ` sjames at gcc dot gnu.org
2023-11-23 15:29 ` post+gcc at ralfj dot de
2023-11-23 18:55 ` bugdal at aerifal dot cx
2023-11-23 19:04 ` post+gcc at ralfj dot de
2023-11-23 20:27 ` bugdal at aerifal dot cx
2023-11-24 8:19 ` public at timruffing dot de
2023-11-24 9:29 ` rguenth at gcc dot gnu.org
2023-11-24 10:09 ` jakub at gcc dot gnu.org
2023-11-24 19:08 ` post+gcc at ralfj dot de
2023-11-27 14:12 ` post+gcc at ralfj dot de
2023-11-27 23:32 ` joseph at codesourcery dot com
2023-11-28 7:17 ` post+gcc at ralfj dot de
2023-11-28 7:20 ` post+gcc at ralfj dot de
2023-11-28 10:58 ` rguenther at suse dot de
2023-11-28 11:03 ` rguenth at gcc dot gnu.org
2023-11-28 11:07 ` fw at gcc dot gnu.org
2024-01-04 12:52 ` rearnsha at gcc dot gnu.org
2024-01-04 13:22 ` bugdal at aerifal dot cx
2024-01-04 13:37 ` jakub at gcc dot gnu.org
2024-01-04 14:28 ` rearnsha at gcc dot gnu.org
2024-01-04 14:29 ` bugdal at aerifal dot cx
2024-01-04 14:41 ` rearnsha at gcc dot gnu.org
2024-01-04 14:44 ` bugdal at aerifal dot cx
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=bug-32667-4-RPoQbCLNJP@http.gcc.gnu.org/bugzilla/ \
--to=gcc-bugzilla@gcc.gnu.org \
--cc=gcc-bugs@gcc.gnu.org \
/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).