From: Peter Maydell <peter.maydell@linaro.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: QEMU Developers <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [PATCH for 2.5] QEMU does not care about left shifts of signed negative values
Date: Tue, 17 Nov 2015 12:22:49 +0000 [thread overview]
Message-ID: <CAFEAcA-XTH7OS_TPYV=Xb-3RSEZRDfUGOs+prbgZ92KVHtLC6A@mail.gmail.com> (raw)
In-Reply-To: <564B193C.9070901@redhat.com>
On 17 November 2015 at 12:10, Paolo Bonzini <pbonzini@redhat.com> wrote:
> On 17/11/2015 12:22, Peter Maydell wrote:
>> * gcc need to document this (this is a stronger statement than
>> what they currently have since it is a guarantee not to change
>> the semantics in the future if -fwrapv is set)
>
> Actually they document it under -fstrict-overflow ("Using '-fwrapv'
> means that integer signed overflow is fully defined: it wraps") but it
> would be nice to add it under -fwrapv as well. I'll send a patch.
My interpretation of that quote was that the gcc devs don't include
shifts in their definition of "integer signed overflows" (since
-fwrapv is very clear about what it affects.) Either way clarity
would be good, so thanks for taking on the patch.
thanks
-- PMM
next prev parent reply other threads:[~2015-11-17 12:23 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-17 9:59 [Qemu-devel] [PATCH for 2.5] QEMU does not care about left shifts of signed negative values Paolo Bonzini
2015-11-17 10:19 ` Peter Maydell
2015-11-17 10:28 ` Paolo Bonzini
2015-11-17 10:36 ` Peter Maydell
2015-11-17 10:37 ` Paolo Bonzini
2015-11-17 10:42 ` Peter Maydell
2015-11-17 10:55 ` Peter Maydell
2015-11-17 10:57 ` Paolo Bonzini
2015-11-17 11:22 ` Peter Maydell
2015-11-17 12:10 ` Paolo Bonzini
2015-11-17 12:22 ` Peter Maydell [this message]
2015-11-17 10:41 ` Laszlo Ersek
2015-11-17 10:43 ` Paolo Bonzini
2015-11-17 10:52 ` Laszlo Ersek
2015-11-17 11:59 ` Markus Armbruster
2015-11-17 12:04 ` Peter Maydell
2015-11-17 12:17 ` Laszlo Ersek
2015-11-17 13:48 ` Paolo Bonzini
2015-11-17 12:18 ` Laszlo Ersek
2015-11-17 10:26 ` Markus Armbruster
2015-11-17 10:36 ` Laszlo Ersek
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