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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 473C2C433FE for ; Thu, 18 Nov 2021 16:27:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 35F2A61A62 for ; Thu, 18 Nov 2021 16:27:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233313AbhKRQaU (ORCPT ); Thu, 18 Nov 2021 11:30:20 -0500 Received: from mail.kernel.org ([198.145.29.99]:32968 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233284AbhKRQaT (ORCPT ); Thu, 18 Nov 2021 11:30:19 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id F0FE961B3A; Thu, 18 Nov 2021 16:27:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1637252839; bh=BKVKyK0RlVmHW5sfIELd2vWo+bvbaMsuAw2qnj28Ue0=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=Ze+6hgboZl91trBQhNlBH077hrKXNgtwB6YfrpkbRCYgLPgZJ7ozp+hHd56FHqXjJ pm4H82eHZSfXbeGJkCzsQatDC5i2IbgjF1Kv1Xj6Bb1X+C9LdQwbVD9JsVnb3K0o/k 71CsuygyZTMzp6QhFIvN/YfCmb+QlGQ41aqPEv4C5+MeD0eJMVNfcpXytDtATCKzyd flpSNnQGQsD3sHvPJocK2isgUWy1BzN1T9RbzoFHctJPglHk3O4JVVv/ifxkZGeRjc ZXpVA/fBP/noYRsX6F25J4zLeb+pFXxdro0ZXgIhfO4cNiB9WCvzb4mFyFJbJWCzdp GRNLUoYQ1W0qA== Received: by mail-wr1-f43.google.com with SMTP id d27so12660395wrb.6; Thu, 18 Nov 2021 08:27:18 -0800 (PST) X-Gm-Message-State: AOAM531u3xzm912I+65umjNtDeMTYjOQch0PQNpmfcdHNWF/sxYYDtS7 8ojW6Z4E36pxoBtNDGr/WW9RZ6Kfke75UYRkBmc= X-Google-Smtp-Source: ABdhPJxqq79QoLh4sUptBU5OL4FavBN2lAtrn/gnM+dcbHtabFve0M/Wdkl43chENdBC2FQ4OXkwCdIHmrQ8McCzDtc= X-Received: by 2002:adf:f088:: with SMTP id n8mr32462459wro.411.1637252837334; Thu, 18 Nov 2021 08:27:17 -0800 (PST) MIME-Version: 1.0 References: <20211118142124.526901-1-arnd@kernel.org> In-Reply-To: From: Arnd Bergmann Date: Thu, 18 Nov 2021 17:27:01 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] [v3] iwlwifi: pcie: fix constant-conversion warning To: Nathan Chancellor Cc: Luca Coelho , Kalle Valo , Arnd Bergmann , kernel test robot , Nick Desaulniers , "David S. Miller" , Jakub Kicinski , Johannes Berg , Yaara Baruch , Matti Gottlieb , Emmanuel Grumbach , linux-wireless , Networking , Linux Kernel Mailing List , llvm@lists.linux.dev Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 18, 2021 at 5:03 PM Nathan Chancellor wrote: > > On Thu, Nov 18, 2021 at 03:21:02PM +0100, Arnd Bergmann wrote: > > From: Arnd Bergmann > > > > gcc-11 points out a potential issue with integer overflow when > > the iwl_dev_info_table[] array is empty: > > > > drivers/net/wireless/intel/iwlwifi/pcie/drv.c:1344:42: error: implicit conversion from 'unsigned long' to 'int' changes value from 18446744073709551615 to -1 [-Werror,-Wconstant-conversion] > > for (i = ARRAY_SIZE(iwl_dev_info_table) - 1; i >= 0; i--) { > > ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~ > > For what it's worth, I do see this warning with Clang when both > CONFIG_IWLDVM and CONFIG_IWLMVM are disabled and looking through the GCC > warning docs [1], I do not see a -Wconstant-conversion option? Maybe > there is another warning that is similar but that warning right there > appears to have come from clang, as it matches mine exactly. > > drivers/net/wireless/intel/iwlwifi/pcie/drv.c:1344:42: error: implicit conversion from 'unsigned long' to 'int' changes value from 18446744073709551615 to -1 [-Werror,-Wconstant-conversion] > for (i = ARRAY_SIZE(iwl_dev_info_table) - 1; i >= 0; i--) { > ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~ > 1 error generated. > > [1]: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html Ok, got it: it turns out this warning /also/ happens with gcc-11 and the initial changelog was the one for matching the clang warning. This is the gcc output, which is very similar but has a different warning option. drivers/net/wireless/intel/iwlwifi/pcie/drv.c: In function 'iwl_pci_find_dev_info': include/linux/kernel.h:46:25: error: overflow in conversion from 'long unsigned int' to 'int' changes value from '18446744073709551615' to '-1' [-Werror=overflow] 46 | #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr)) | ^ drivers/net/wireless/intel/iwlwifi/pcie/drv.c:1344:18: note: in expansion of macro 'ARRAY_SIZE' 1344 | for (i = ARRAY_SIZE(iwl_dev_info_table) - 1; i >= 0; i--) { My v2 patch only addressed the clang warning, while v3 works with both gcc and clang. I can send a v4 if I should update the changelog again to explain that, but I suppose it's still close enough. Arnd