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[109.217.237.144]) by smtp.gmail.com with ESMTPSA id r13sm12325205wrn.2.2021.05.03.00.40.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 03 May 2021 00:40:45 -0700 (PDT) Subject: Re: [PATCH 1/4] pc-bios/s390-ccw: Silence warning from Clang by marking panic() as noreturn To: Thomas Huth , qemu-s390x@nongnu.org, Christian Borntraeger References: <20210502174836.838816-1-thuth@redhat.com> <20210502174836.838816-2-thuth@redhat.com> <04140977-282c-2579-3073-42b6bb4148ee@redhat.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: <70298aa0-c3fe-030c-23d5-d535bb56f6f3@redhat.com> Date: Mon, 3 May 2021 09:40:42 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=philmd@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=philmd@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, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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: Cornelia Huck , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 5/3/21 6:53 AM, Thomas Huth wrote: > On 02/05/2021 20.57, Philippe Mathieu-Daudé wrote: >> On 5/2/21 7:48 PM, Thomas Huth wrote: >>> When compiling the s390-ccw bios with Clang, the compiler emits a >>> warning: >>> >>>   pc-bios/s390-ccw/main.c:210:5: warning: variable 'found' is used >>> uninitialized >>>    whenever switch default is taken [-Wsometimes-uninitialized] >>>       default: >>>       ^~~~~~~ >>>   pc-bios/s390-ccw/main.c:214:16: note: uninitialized use occurs here >>>       IPL_assert(found, "Boot device not found\n"); >>>                  ^~~~~ >>> >>> It's a false positive, it only happens because Clang is not smart enough >>> to see that the panic() function in the "default:" case can never >>> return. >>> >>> Anyway, let's explicitely mark panic() with "noreturn" to shut up the >>> warning. >> >> Why not simply initialize the variable instead? > > First, it's a false positive. If you only look at the code, someone > might later wonder whether it's really necessary or not and try to > remove it again (and since there is no warning with gcc, this patch > would also have a good chance to get merged, bringing us back to where > we are right now). > > Second, declaring panic() as noreturn is certainly more sustainable, > since it might prevent similar situations in other parts of the code in > the future. Fine then: Reviewed-by: Philippe Mathieu-Daudé