public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/108718] [10/11/12/13 Regression] csmith: possible bad code with -O2
Date: Thu, 09 Feb 2023 20:12:26 +0000	[thread overview]
Message-ID: <bug-108718-4-H6l86v0vUC@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-108718-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108718

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to David Binderman from comment #4)
> (In reply to Andrew Pinski from comment #3)
> > This also changes with  -fno-strict-aliasing  ...
> 
> So does that mean that csmith is producing C code with UB and so
> this bug isn't valid ?

Not necessarily.  If something misbehaves with -O2 and behaves as expected with
-O2 -fno-strict-aliasing, then it is usually a good sign that there is or might
be an aliasing violation, but it isn't a proof that there is one.  Only
detailed analysis of the code or e.g. the latter only focused on what exactly
changes with the bisection point can reveal if it is or isn't valid.

  parent reply	other threads:[~2023-02-09 20:12 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-08 13:53 [Bug c/108718] New: " dcb314 at hotmail dot com
2023-02-08 14:06 ` [Bug c/108718] " jakub at gcc dot gnu.org
2023-02-08 14:12 ` [Bug c/108718] [10/11/12/13 Regression] " jakub at gcc dot gnu.org
2023-02-08 17:06 ` pinskia at gcc dot gnu.org
2023-02-09 15:10 ` dcb314 at hotmail dot com
2023-02-09 20:12 ` jakub at gcc dot gnu.org [this message]
2023-02-10 10:19 ` rguenth at gcc dot gnu.org
2023-02-10 17:07 ` dcb314 at hotmail dot com
2023-02-15  8:17 ` dcb314 at hotmail dot com
2023-02-15 10:29 ` dcb314 at hotmail dot com
2023-02-15 10:39 ` marxin at gcc dot gnu.org
2023-02-15 17:00 ` dcb314 at hotmail dot com
2023-02-16 12:59 ` jakub at gcc dot gnu.org

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-108718-4-H6l86v0vUC@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).