From patchwork Mon Oct 26 21:52:56 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Arnd Bergmann X-Patchwork-Id: 11858899 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 954EE1130 for ; Mon, 26 Oct 2020 21:53:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7CBC921707 for ; Mon, 26 Oct 2020 21:53:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603749212; bh=cbvz8JZpRk6jgUksGk7xL97fNKKDmg9abo4AHqnljqE=; h=From:To:Cc:Subject:Date:List-ID:From; b=MqYhU8CZjTX/hqdcAfuCvk5naigcvBWXDZsZ7Qvgs/A1If1+KF0i5PGsnbz5lD2F8 22yAOVHQ2dhZaWMs6IlK2RJT08Pp3ilYOW5qnFin6Iz0nT6b1QdmlJeg7xxjSlwZ+K 8cv8LGpxjwvrDfChkhAaOvUgjtroxuUe3+Wzjf3M= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391063AbgJZVx3 (ORCPT ); Mon, 26 Oct 2020 17:53:29 -0400 Received: from mail.kernel.org ([198.145.29.99]:52572 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391058AbgJZVx2 (ORCPT ); Mon, 26 Oct 2020 17:53:28 -0400 Received: from localhost.localdomain (unknown [192.30.34.233]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 443852084C; Mon, 26 Oct 2020 21:53:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603749208; bh=cbvz8JZpRk6jgUksGk7xL97fNKKDmg9abo4AHqnljqE=; h=From:To:Cc:Subject:Date:From; b=sRv3EjZur1PCPWhhj3mdgNha05v1M2MO1n/C3QZ7d2HyClMSDBGuYjcwreXwAsxn+ IMHaDbYbvkwvvSLHQEaesminOpgedDGwc4KNOCEqAODKQXa2j2qGkyqRiGtOo60imy bl0plDlCdKtBqZo3GC5uXKq0wQQavhw03XU38t1A= From: Arnd Bergmann To: Greg Kroah-Hartman , Tejun Heo , Alexander Viro , Nathan Chancellor , Nick Desaulniers Cc: Arnd Bergmann , Amir Goldstein , Jan Kara , Andrew Morton , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, clang-built-linux@googlegroups.com Subject: [PATCH] seq_file: fix clang warning for NULL pointer arithmetic Date: Mon, 26 Oct 2020 22:52:56 +0100 Message-Id: <20201026215321.3894419-1-arnd@kernel.org> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Arnd Bergmann Clang points out that adding something to NULL is notallowed in standard C: fs/kernfs/file.c:127:15: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] return NULL + !*ppos; ~~~~ ^ fs/seq_file.c:529:14: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] return NULL + (*pos == 0); Rephrase the function to do the same thing without triggering that warning. Linux already relies on a specific binary representation of NULL, so it makes no real difference here. The instance in kernfs was copied from single_start, so fix both at once. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Fixes: c2b19daf6760 ("sysfs, kernfs: prepare read path for kernfs") Signed-off-by: Arnd Bergmann Reviewed-by: Nathan Chancellor --- fs/kernfs/file.c | 2 +- fs/seq_file.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c index f277d023ebcd..b55e6ef4d677 100644 --- a/fs/kernfs/file.c +++ b/fs/kernfs/file.c @@ -124,7 +124,7 @@ static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos) * The same behavior and code as single_open(). Returns * !NULL if pos is at the beginning; otherwise, NULL. */ - return NULL + !*ppos; + return (void *)(uintptr_t)!*ppos; } } diff --git a/fs/seq_file.c b/fs/seq_file.c index 31219c1db17d..d456468eb934 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -526,7 +526,7 @@ EXPORT_SYMBOL(seq_dentry); static void *single_start(struct seq_file *p, loff_t *pos) { - return NULL + (*pos == 0); + return (void *)(uintptr_t)(*pos == 0); } static void *single_next(struct seq_file *p, void *v, loff_t *pos)