public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "jhubbard at nvidia dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/101645] warn about neg of unsigned type should be added to -Wsign-conversion
Date: Tue, 27 Jul 2021 21:27:45 +0000	[thread overview]
Message-ID: <bug-101645-4-IrnGaM47nt@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-101645-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101645

John Hubbard <jhubbard at nvidia dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jhubbard at nvidia dot com

--- Comment #3 from John Hubbard <jhubbard at nvidia dot com> ---
Here are some data points in favor of adding this warning:

1) It's already desirable in a real project (Linux kernel, as Matthew pointed
out), and

2) Clang has already gone there, presumably for good reasons as well.

3) Anecdote: as an experienced C programmer, I can tell you that the "b(-x)"
results are rarely what a programmer would want, nor intend. (Of course, the
ideal is a perfect type-safe match between input and args, but that doesn't
always happen in real code.)

The compiler knows enough to significantly help here, by warning. It's also
possible to update the -Wsign-conversion documentation to match, if necessary,
let's not forget that.

  parent reply	other threads:[~2021-07-27 21:27 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-27 15:21 [Bug c/101645] New: -Wsign-conversion misses negation of unsigned int matthew at wil dot cx
2021-07-27 15:27 ` [Bug c/101645] " jrtc27 at jrtc27 dot com
2021-07-27 19:06 ` [Bug c/101645] warn about neg of unsigned type should be added to -Wsign-conversion pinskia at gcc dot gnu.org
2021-07-27 21:27 ` jhubbard at nvidia dot com [this message]
2021-07-28 12:35 ` matthew at wil dot cx
2021-07-28 17:55 ` redi 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-101645-4-IrnGaM47nt@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).