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References: <38A2C2D0FB356A4785EEFA56D99BFB2B0B718883@SHSMSX101.ccr.corp.intel.com>
From: Thomas Huth <thuth@redhat.com>
Message-ID: <14b75ee9-7a5f-eb69-f210-f7b2e72cbaf8@redhat.com>
Date: Thu, 28 Feb 2019 17:41:59 +0100
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Subject: Re: [Qemu-devel] Qemu build failure with uninitialized variables
 when "-Wmaybe-uninitialized" is open
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To: "Wei, Danmei" <danmei.wei@intel.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Cc: "Hao, Xudong" <xudong.hao@intel.com>

On 28/02/2019 04.00, Wei, Danmei wrote:
> Hi,
> 
> When we build qemu with "-Wmaybe-uninitialized" on, and got the following error information.
>   CC      qobject/json-streamer.o
>   CC      qobject/json-parser.o
>   CC      qobject/block-qdict.o
> qobject/block-qdict.c: In function 'qdict_array_split':
> qobject/block-qdict.c:259:25: error: 'subqdict' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>          qlist_append_obj(*dst, subqobj ?: QOBJECT(subqdict));
>                          ^
> cc1: all warnings being treated as errors
> make: *** [qobject/block-qdict.o] Error 1
> 
> It is because of the uninitialized variable subqdict function qdict_array_split.
> Thanks to confirm it.
> 
> Below is the ENV Setting:
> OS: RHEL OS 7.6
> Qemu Version: commit c102d9471f8f02d9fbea72ec4505d7089173f470
> CFLAGS Setting in env: export CFLAGS="-g -O3 -Wmaybe-uninitialized"

Don't build QEMU with -O3 and -Wmaybe-uninitialized and -Werror
together. -O3 produces lots of false warnings with
-Wmaybe-uninitialized, so we currently don't support building QEMU with
that combination. You should at least add
"-Wno-error=maybe-uninitialized" if you want to build that way.

 Thomas