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From: Anthony Liguori <anthony@codemonkey.ws>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: QEMU Trivial <qemu-trivial@nongnu.org>,
	Stefan Hajnoczi <stefanha@gmail.com>,
	Anthony Liguori <aliguori@us.ibm.com>,
	qemu-devel@nongnu.org, Stefan Weil <sw@weilnetz.de>
Subject: Re: [Qemu-devel] [PATCH] vnc: Fix packed boolean struct members
Date: Thu, 08 Mar 2012 10:25:19 -0600	[thread overview]
Message-ID: <4F58DD6F.8080907@codemonkey.ws> (raw)
In-Reply-To: <4F58D961.70706@redhat.com>

On 03/08/2012 10:08 AM, Paolo Bonzini wrote:
> Il 08/03/2012 16:26, Stefan Hajnoczi ha scritto:
>> I had to drop this patch from the trivial patches tree, it tickles a
>> new gcc warning.  Please resend with the necessary change.
>>
>> I cannot reproduce it on my build host here with gcc Debian 4.6.2-12
>> but Anthony reports the following Ubuntu/Linaro 4.5.2-8ubuntu4:
>>
>>    CC    ui/vnc-auth-sasl.o
>> cc1: warnings being treated as errors
>> /home/anthony/git/qemu/ui/vnc-auth-sasl.c: In function
>> ‘vnc_sasl_client_cleanup’:
>> /home/anthony/git/qemu/ui/vnc-auth-sasl.c:34:9: error: suggest
>> parentheses around assignment used as truth value
>> make: *** [ui/vnc-auth-sasl.o] Error 1
>
> Looks like a GCC bug where
>
>     x = y = 0;
>
> is converted to
>
>     x = (y = 0) != 0;

Curious, why convert like this?  What does this optimization do?

Regards,

Anthony Liguori

>
> and the magic that does this inside the compiler causes the warning.
>
> We should add a configure check to only add -Werror on compilers newer
> than X (for example X could leave out GCC 4.5), so that this patch can
> be reapplied.
>
> Paolo
>

  reply	other threads:[~2012-03-08 16:25 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-02-25 13:35 [Qemu-devel] [PATCH] vnc: Fix packed boolean struct members Stefan Weil
2012-03-05 13:15 ` Stefan Hajnoczi
2012-03-08 15:26 ` Stefan Hajnoczi
2012-03-08 16:08   ` Paolo Bonzini
2012-03-08 16:25     ` Anthony Liguori [this message]
2012-03-08 18:07       ` Paolo Bonzini

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