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Mon, 3 May 2021 06:56:24 +0200 (CEST) From: Markus Armbruster To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Subject: Re: [PATCH 1/4] pc-bios/s390-ccw: Silence warning from Clang by marking panic() as noreturn References: <20210502174836.838816-1-thuth@redhat.com> <20210502174836.838816-2-thuth@redhat.com> <04140977-282c-2579-3073-42b6bb4148ee@redhat.com> Date: Mon, 03 May 2021 06:56:24 +0200 In-Reply-To: <04140977-282c-2579-3073-42b6bb4148ee@redhat.com> ("Philippe =?utf-8?Q?Mathieu-Daud=C3=A9=22's?= message of "Sun, 2 May 2021 20:57:02 +0200") Message-ID: <87v980fm9z.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=216.205.24.124; envelope-from=armbru@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=-0.01, 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: Christian Borntraeger , Thomas Huth , Cornelia Huck , qemu-s390x@nongnu.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Philippe Mathieu-Daud=C3=A9 writes: > On 5/2/21 7:48 PM, Thomas Huth wrote: >> When compiling the s390-ccw bios with Clang, the compiler emits a warnin= g: >>=20 >> pc-bios/s390-ccw/main.c:210:5: warning: variable 'found' is used uninit= ialized >> 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"); >> ^~~~~ >>=20 >> 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= . >>=20 >> Anyway, let's explicitely mark panic() with "noreturn" to shut up the >> warning. > > Why not simply initialize the variable instead? Because telling an optimizing compiler the truth is a good idea?