From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Roger Pau Monne <roger.pau@citrix.com>, xen-devel@lists.xenproject.org
Subject: Re: [PATCH 2/3] xtf: avoid shifting a negative value
Date: Fri, 6 May 2016 15:57:26 +0100 [thread overview]
Message-ID: <572CB0D6.8020403@citrix.com> (raw)
In-Reply-To: <1462544723-48415-3-git-send-email-roger.pau@citrix.com>
On 06/05/16 15:25, Roger Pau Monne wrote:
> Because it's undefined behaviour.
>
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
> ---
> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> ---
> include/arch/x86/processor.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/arch/x86/processor.h b/include/arch/x86/processor.h
> index c9f253f..841953c 100644
> --- a/include/arch/x86/processor.h
> +++ b/include/arch/x86/processor.h
> @@ -134,7 +134,7 @@
> /* Segment-based Error Code - supplemental constants. */
> #define X86_EC_TABLE_MASK (3 << 1)
> #define X86_EC_SEL_SHIFT 3
> -#define X86_EC_SEL_MASK (-1 << X86_EC_SEL_SHIFT)
> +#define X86_EC_SEL_MASK (-1U << X86_EC_SEL_SHIFT)
The resulting expression needs to be signed, to DTRT when implicitly
promoted. I presume this was clang complaining?
Does using the constant (-9) work?
~Andrew
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next prev parent reply other threads:[~2016-05-06 14:57 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-06 14:25 [PATCH 0/3] XTF: small fixes Roger Pau Monne
2016-05-06 14:25 ` [PATCH 1/3] xtf: don't re-define __noinline Roger Pau Monne
2016-05-06 14:25 ` [PATCH 2/3] xtf: avoid shifting a negative value Roger Pau Monne
2016-05-06 14:57 ` Andrew Cooper [this message]
2016-05-06 15:05 ` Andrew Cooper
2016-05-06 14:25 ` [PATCH 3/3] xtf: fix usage of "-executable" with find Roger Pau Monne
2016-05-06 14:46 ` [PATCH 0/3] XTF: small fixes Andrew Cooper
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