From: Paolo Bonzini <pbonzini@redhat.com>
To: John Snow <jsnow@redhat.com>
Cc: qemu-devel@nongnu.org, qemu-trivial@nongnu.org,
kraxel@redhat.com, peter maydell <peter.maydell@linaro.org>
Subject: Re: [Qemu-devel] [PATCH] Remove left shifts of negative signed integers
Date: Thu, 30 Jun 2016 16:32:59 -0400 (EDT) [thread overview]
Message-ID: <1978695732.3315031.1467318779611.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <5b24e821-7b08-257b-0b3e-0e3336ee644c@redhat.com>
> > GCC correctly puts this warning under -Wextra, and promises not to ever
> > make use of this facet of undefined behavior. The only correct patch
> > is the one that disables the warning for clang, and possibly adds
> > -fwrapv. In GCC, -fwrapv correctly silences ubsan's left-shift
> > and signed-overflow warnings. In Clang, this is reported at
> > https://llvm.org/bugs/show_bug.cgi?id=25552. It's a heavy hammer
> > but it's the safest options as compiler evolve.
>
> Where /exactly/ do you propose we canonicalize the clang invocation you
> would like to support?
In configure where we look for other warning flags. Add -fwrapv and
-Wno-shift-negative-value so that they're enabled if the compilers
supports them.
Paolo
next prev parent reply other threads:[~2016-06-30 20:33 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-30 19:36 [Qemu-devel] [PATCH] Remove left shifts of negative signed integers John Snow
2016-06-30 20:11 ` Peter Maydell
2016-06-30 20:13 ` John Snow
2016-06-30 20:16 ` Paolo Bonzini
2016-06-30 20:15 ` Paolo Bonzini
2016-06-30 20:20 ` John Snow
2016-06-30 20:32 ` Paolo Bonzini [this message]
2016-08-16 14:00 ` Peter Maydell
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=1978695732.3315031.1467318779611.JavaMail.zimbra@redhat.com \
--to=pbonzini@redhat.com \
--cc=jsnow@redhat.com \
--cc=kraxel@redhat.com \
--cc=peter.maydell@linaro.org \
--cc=qemu-devel@nongnu.org \
--cc=qemu-trivial@nongnu.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 NNTP newsgroup(s).