From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0AF7DC48260 for ; Tue, 13 Feb 2024 19:20:00 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4TZB3f4DHGz3vYX for ; Wed, 14 Feb 2024 06:19:58 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.crashing.org (client-ip=63.228.1.57; helo=gate.crashing.org; envelope-from=segher@kernel.crashing.org; receiver=lists.ozlabs.org) Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by lists.ozlabs.org (Postfix) with ESMTP id 4TZB364jc0z2xWR for ; Wed, 14 Feb 2024 06:19:29 +1100 (AEDT) Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 41DJCu2k018865; Tue, 13 Feb 2024 13:12:56 -0600 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 41DJCtmj018864; Tue, 13 Feb 2024 13:12:55 -0600 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Tue, 13 Feb 2024 13:12:54 -0600 From: Segher Boessenkool To: Arnd Bergmann Subject: Re: [PATCH] tty: hvc-iucv: fix function pointer casts Message-ID: <20240213191254.GA19790@gate.crashing.org> References: <20240213101756.461701-1-arnd@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240213101756.461701-1-arnd@kernel.org> User-Agent: Mutt/1.4.2.3i X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, Arnd Bergmann , Greg Kroah-Hartman , llvm@lists.linux.dev, Nick Desaulniers , linux-kernel@vger.kernel.org, Nathan Chancellor , Bill Wendling , linux-serial@vger.kernel.org, Justin Stitt , Jiri Slaby Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, Feb 13, 2024 at 11:17:49AM +0100, Arnd Bergmann wrote: > clang warns about explicitly casting between incompatible function > pointers: > > drivers/tty/hvc/hvc_iucv.c:1100:23: error: cast from 'void (*)(const void *)' to 'void (*)(struct device *)' converts to incompatible function type [-Werror,-Wcast-function-type-strict] > 1100 | priv->dev->release = (void (*)(struct device *)) kfree; > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Such a cast of course is explicitly allowed by 6.3.2.3/8, only calling a function using a non-compatible type is UB. This warning message is quite misleading. Doubly so because of the -Werror, as always. Your proposed new code of course is nice and simple (albeit a bit bigger than it was before, both source and binary). Such is life ;-) Segher