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[217.232.61.128]) by smtp.gmail.com with ESMTPSA id f18sm20057897wmj.13.2021.06.09.00.12.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 09 Jun 2021 00:12:27 -0700 (PDT) Subject: Re: Prevent compiler warning on block.c To: Vladimir Sementsov-Ogievskiy , Miroslav Rezanina , QEMU Developers References: <1162368493.17178530.1620201543649.JavaMail.zimbra@redhat.com> <62c90da0-b2f9-7068-e84f-c13bb1527191@virtuozzo.com> From: Thomas Huth Message-ID: <9ef22266-25e1-36df-52e9-ad5244a648dc@redhat.com> Date: Wed, 9 Jun 2021 09:12:26 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <62c90da0-b2f9-7068-e84f-c13bb1527191@virtuozzo.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=thuth@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=thuth@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.197, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , QEMU Trivial , Cleber Rosa , qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 05/05/2021 10.05, Vladimir Sementsov-Ogievskiy wrote: > 05.05.2021 10:59, Miroslav Rezanina wrote: >> Commit 3108a15cf (block: introduce bdrv_drop_filter()) introduced >> uninitialized >> variable to_cow_parent in bdrv_replace_node_common function that is used >> only when >> detach_subchain is true. It is used in two places. First if block properly >> initialize >> the variable and second block use it. >> >> However, compiler treats this two blocks as two independent cases so it >> thinks first >> block can fail test and second one pass (although both use same >> condition). This cause >> warning that variable can be uninitialized in second block. >> >> To prevent this warning, initialize the variable with NULL. >> >> Signed-off-by: Miroslav Rezanina >> --- >> diff --git a/block.c b/block.c >> index 874c22c43e..3ca27bd2d9 100644 >> --- a/block.c >> +++ b/block.c >> @@ -4851,7 +4851,7 @@ static int bdrv_replace_node_common(BlockDriverState >> *from, >>       Transaction *tran = tran_new(); >>       g_autoptr(GHashTable) found = NULL; >>       g_autoptr(GSList) refresh_list = NULL; >> -    BlockDriverState *to_cow_parent; >> +    BlockDriverState *to_cow_parent = NULL; >>       int ret; >> >>       if (detach_subchain) { >> > > Reviewed-by: Vladimir Sementsov-Ogievskiy This just popped up again here: https://lists.gnu.org/archive/html/qemu-devel/2021-06/msg02067.html Kevin, Max, could you please pick it up to get this problem fixed? Thomas