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Wed, 5 May 2021 11:12:35 +0000 (UTC) Date: Wed, 5 May 2021 07:12:35 -0400 (EDT) From: Miroslav Rezanina To: Peter Maydell Message-ID: <1691168205.17503177.1620213155446.JavaMail.zimbra@redhat.com> In-Reply-To: References: <603798381.17174916.1620200426349.JavaMail.zimbra@redhat.com> <1162368493.17178530.1620201543649.JavaMail.zimbra@redhat.com> Subject: Re: Prevent compiler warning on block.c MIME-Version: 1.0 X-Originating-IP: [10.40.192.172, 10.4.195.16] Thread-Topic: Prevent compiler warning on block.c Thread-Index: yTgQvcpIyuAgj99B+cUmdNHc62gLlA== X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mrezanin@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=mrezanin@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.697, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, 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=ham 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: Vladimir Sementsov-Ogievskiy , QEMU Developers , Qemu-block Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" ----- Original Message ----- > From: "Peter Maydell" > To: "Miroslav Rezanina" > Cc: "QEMU Developers" , "Vladimir Sementsov-Ogievskiy" , > "Qemu-block" > Sent: Wednesday, May 5, 2021 12:43:44 PM > Subject: Re: Prevent compiler warning on block.c > > On Wed, 5 May 2021 at 09:06, 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. > > If fixing compiler warnings, please quote the compiler name/version > in the commit message. (This helps with understanding whether the issue > is because of an older and not-smart-enough compiler or a new bleeding-edge > compiler with extra checking.) Hi Peter, sorry for missing version. I was going to put the version in but got distracted when checking versions. This warning occurs using GCC 8.4.1 and 11.0.1. Mirek > > thanks > -- PMM > > -- Miroslav Rezanina Software Engineer - Virtualization Team Maintainer