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Date: Sat, 07 Mar 2015 10:50:19 +0100
From: Stefan Weil <sw@weilnetz.de>
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Subject: Re: [Qemu-devel] clang warnings too noisy
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To: Stefan Hajnoczi <stefanha@gmail.com>, Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-devel <qemu-devel@nongnu.org>

Am 07.03.2015 um 10:04 schrieb Stefan Weil:
> Am 06.03.2015 um 20:06 schrieb Stefan Hajnoczi:
>> Hi Peter,
>> You are rejecting pull requests that produce warnings under clang.
>>
>> clang 3.5.0 on Fedora 21 produces so much noise that it's extremely
>> tedious and error-prone to try finding relevant new warnings.
>>
>> Are you using a different clang version which produces fewer warnings?
>>
>> Is anyone working on making QEMU build cleanly under clang? Under gcc
>> people regularly submit patches to keep the build clean (e.g. recent
>> gcc 5 fixes).
>>
>> Currently I'm not happy wrangling with clang when very few people seem
>> to use it or care enough to make QEMU build cleanly.
>>
>
> Compilation with different compilers is still very important to detect 
> hidden bugs. Here is the latest example which I found because of your 
> e-mail:
>
> block/iscsi.c:1329:20: warning: comparison of array 'iscsi_url->user' 
> not equal to a null pointer is always true 
> [-Wtautological-pointer-compare]
>
> The code is wrong (I'll send a patch), and the code where it was 
> copied from is wrong, too (see 
> https://github.com/sahlberg/libiscsi/pull/146).
>
> I use clang on Mac from time to time and used it some time ago on Linux.
>
> Regards
> Stefan

My clang build (Debian Jessie clang version 3.5.0-10 
(tags/RELEASE_350/final) (based on LLVM 3.5.0))
just found one more bug and also an unused variable (patches already 
sent to qemu-devel), therefore
yes, we need it.

Stefan