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 D02B9C433F5 for ; Mon, 14 Feb 2022 17:00:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1356862AbiBNRBA (ORCPT ); Mon, 14 Feb 2022 12:01:00 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:38432 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356810AbiBNRA5 (ORCPT ); Mon, 14 Feb 2022 12:00:57 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2C94665166 for ; Mon, 14 Feb 2022 09:00:50 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id B511B6152F for ; Mon, 14 Feb 2022 17:00:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A1318C340E9; Mon, 14 Feb 2022 17:00:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1644858049; bh=PI1oi4wqJp519f7VqcJNgQaXQZ5sP53GHooYRli1yx0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=lVCFfnn+5uB5WbG+//QIsvejjCnxpXGGNv8XZ9wHR+OtGcFra+91eRvbXQUn8Duu/ DTSD0fKrJZzx15b8GX88EA/Zytm8y+3AVfIEc0avsjrUPcPbiWGljVf/fNl6gWYoax jF8KSThmw4e4VMlPLYU+8UvRPNqdo9+YxtZ6Axm5BpAVE6rDL0BJwipGpe1E9tFbvY NoG6CaCkdazCmsc/qJKhZlVXNQoFe7fYoXQlQMj+3HMmGCQ4appzqVid4aP1YeUajW 1v2B5dB/Wv/h/hF3IGjwtegxqdDRjNDWURcng+ScX7r6yTbg/9Z8GTWbjb8/2AoMZi OATPkIstL9Udw== Date: Mon, 14 Feb 2022 10:00:44 -0700 From: Nathan Chancellor To: Masahiro Yamada Cc: Steven Rostedt , kernel test robot , chongjiapeng , llvm@lists.linux.dev, kbuild-all@lists.01.org, Linux Kernel Mailing List Subject: Re: kernel/trace/ftrace.c:7157:20: error: unused function 'ftrace_startup_enable' Message-ID: References: <202202132037.4aN017dU-lkp@intel.com> <20220214102000.1d3af66e@gandalf.local.home> 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-kernel@vger.kernel.org On Tue, Feb 15, 2022 at 01:28:53AM +0900, Masahiro Yamada wrote: > On Tue, Feb 15, 2022 at 12:53 AM Nathan Chancellor wrote: > > > > Hi Steve, > > > > On Mon, Feb 14, 2022 at 10:20:00AM -0500, Steven Rostedt wrote: > > > On Sun, 13 Feb 2022 21:03:29 +0800 > > > kernel test robot wrote: > > > > > > > All errors (new ones prefixed by >>): > > > > > > > > >> kernel/trace/ftrace.c:7157:20: error: unused function 'ftrace_startup_enable' [-Werror,-Wunused-function] > > > > static inline void ftrace_startup_enable(int command) { } > > > > ^ > > > > 1 error generated. > > > > > > Strange. I always thought that static inline functions do not cause > > > warnings when not used? Especially, since they are often in headers when > > > things are turned off. Or is it because this is in a C file? > > > > With -Wunused-function, clang will warn about unused static inline > > functions within a .c file (but not .h), whereas GCC will not warn for > > either. The unused attribute was added to the definition of inline to > > make clang's behavior match GCC's. > > > > > Is this a new warning caused by a commit, or is it a new warning because > > > the compiler now complains about it? > > > > However, in commit 6863f5643dd7 ("kbuild: allow Clang to find unused > > static inline functions for W=1 build"), Masahiro made it so that the > > unused attribute does not get added at W=1 so that instances of unused > > static inline functions can be caught and eliminated (or put into use, > > if the function should have been used), hence this report. > > BTW, my hope was to move this warning to W=0 someday. > (that is, remove __inline_maybe_unused entirely). > > I do not know how many warnings are still remaining, though. > Is it now more difficult due to CONFIG_WERROR? I have not done an audit in quite a while and I do not remember the results of the last one. I don't think -Werror makes it more difficult, it is more so just finding the time to sit down and work on it :) I agree that it would be nice to make this the default behavior for cleaner code, perhaps we can use this as a "good first issue" for working with clang. Cheers, Nathan