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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CB503C43219 for ; Mon, 28 Feb 2022 23:27:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230087AbiB1X1r (ORCPT ); Mon, 28 Feb 2022 18:27:47 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48356 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229961AbiB1X1p (ORCPT ); Mon, 28 Feb 2022 18:27:45 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DB8CADE2C1; Mon, 28 Feb 2022 15:27:04 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=kySnWHttTi8Odl1WzgGLjQ1pb3b/AWH5qnYZSwnte50=; b=nt03mWtTaEB9qwsFMTflxzDbvW aPSsVBeLr8i8UFwA1l3fNavsuYE231uUwb0yDTUi43cd3zIwbEaMZqro2u+rXbOt0KZriPQpyGi5J +pW6oqM84XOoVppIQh3QNnM4ANpt9aIP3ShEwC0IGa2NKI/m2xxapQAyHhJG42Bevn7SuMSAnyA27 7+3DFdmFFllbJzk1MHudhAJj7GPo/5RsA7npxrePVRbtGBQKbJeOUSye2chevgvDMrFkod2y0FmL7 JW29U+rs2LR5a0WX3s04bvbvXotX/UjRCpaaxaXPYROyoDfpDk5Wuy418QovroPX+qbpGelik5Tc/ I0FC9RZw==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1nOpPe-0090gL-Ex; Mon, 28 Feb 2022 23:26:42 +0000 Date: Mon, 28 Feb 2022 23:26:42 +0000 From: Matthew Wilcox To: Linus Torvalds Cc: Christian =?iso-8859-1?Q?K=F6nig?= , Jakob Koschel , alsa-devel@alsa-project.org, linux-aspeed@lists.ozlabs.org, "Gustavo A. R. Silva" , linux-iio@vger.kernel.org, nouveau@lists.freedesktop.org, Rasmus Villemoes , dri-devel , Cristiano Giuffrida , amd-gfx list , samba-technical@lists.samba.org, linux1394-devel@lists.sourceforge.net, drbd-dev@lists.linbit.com, linux-arch , CIFS , KVM list , linux-scsi , linux-rdma , linux-staging@lists.linux.dev, "Bos, H.J." , Jason Gunthorpe , intel-wired-lan@lists.osuosl.org, kgdb-bugreport@lists.sourceforge.net, bcm-kernel-feedback-list@broadcom.com, Dan Carpenter , Linux Media Mailing List , Kees Cook , Arnd Bergman , Linux PM , intel-gfx , Brian Johannesmeyer , Nathan Chancellor , linux-fsdevel , Christophe JAILLET , v9fs-developer@lists.sourceforge.net, linux-tegra , Thomas Gleixner , Andy Shevchenko , Linux ARM , linux-sgx@vger.kernel.org, linux-block , Netdev , linux-usb@vger.kernel.org, linux-wireless , Linux Kernel Mailing List , Linux F2FS Dev Mailing List , tipc-discussion@lists.sourceforge.net, Linux Crypto Mailing List , dma , linux-mediatek@lists.infradead.org, Andrew Morton , linuxppc-dev , Mike Rapoport Subject: Re: [PATCH 2/6] treewide: remove using list iterator after loop body as a ptr Message-ID: References: <20220228110822.491923-1-jakobkoschel@gmail.com> <20220228110822.491923-3-jakobkoschel@gmail.com> <2e4e95d6-f6c9-a188-e1cd-b1eae465562a@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Feb 28, 2022 at 12:37:15PM -0800, Linus Torvalds wrote: > On Mon, Feb 28, 2022 at 12:16 PM Matthew Wilcox wrote: > > > > Then we can never use -Wshadow ;-( I'd love to be able to turn it on; > > it catches real bugs. > > Oh, we already can never use -Wshadow regardless of things like this. > That bridge hasn't just been burned, it never existed in the first > place. > > The whole '-Wshadow' thing simply cannot work with local variables in > macros - something that we've used since day 1. > > Try this (as a "p.c" file): > > #define min(a,b) ({ \ > typeof(a) __a = (a); \ > typeof(b) __b = (b); \ > __a < __b ? __a : __b; }) > > int min3(int a, int b, int c) > { > return min(a,min(b,c)); > } > > and now do "gcc -O2 -S t.c". > > Then try it with -Wshadow. #define ___PASTE(a, b) a##b #define __PASTE(a, b) ___PASTE(a, b) #define _min(a, b, u) ({ \ typeof(a) __PASTE(__a,u) = (a); \ typeof(b) __PASTE(__b,u) = (b); \ __PASTE(__a,u) < __PASTE(__b,u) ? __PASTE(__a,u) : __PASTE(__b,u); }) #define min(a, b) _min(a, b, __COUNTER__) int min3(int a, int b, int c) { return min(a,min(b,c)); } (probably there's a more elegant way to do this)