From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966966AbdEWSDU (ORCPT ); Tue, 23 May 2017 14:03:20 -0400 Received: from mail-pf0-f181.google.com ([209.85.192.181]:36149 "EHLO mail-pf0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966608AbdEWSDS (ORCPT ); Tue, 23 May 2017 14:03:18 -0400 Date: Tue, 23 May 2017 11:03:16 -0700 From: Matthias Kaehlcke To: Christoph Hellwig Cc: linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: [PATCH] zlib: Put get_unaligned16() inside #ifdef block Message-ID: <20170523180316.GO141096@google.com> References: <20170522211326.66973-1-mka@chromium.org> <20170523073601.GA29525@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20170523073601.GA29525@infradead.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Christoph, El Tue, May 23, 2017 at 12:36:01AM -0700 Christoph Hellwig ha dit: > On Mon, May 22, 2017 at 02:13:26PM -0700, Matthias Kaehlcke wrote: > > The function is not used when CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y. > > Adding the #ifdef fixes the following warning when building with clang: > > > > lib/zlib_inflate/inffast.c:31:1: error: unused function 'get_unaligned16' > > [-Werror,-Wunused-function] > > > > Signed-off-by: Matthias Kaehlcke > > --- > > Note: Usually we would use the __maybe_unused attribute to silence the > > warning. Since this code is used in the kernel decompression stub rather > > than in the kernel itself we can't include with the > > definition of __maybe_unused (it would be possible for some platforms, > > however for powerpc the build fails with a compiler error). We could > > redefine __maybe_unused or use the raw __attribute__((unused)), but > > using the #ifdef is a simpler solution. > > Usually one would take a look at the root cause. And then remove > get_unaligned16 entirely and replace it with the get_unaligned > helper provided by the kernel. Thanks for the suggestion to use get_unaligned(). Unfortunately that doesn't work without hackery, at least for powerpc. We can add arch/powerpc/include to the include paths of the decompression stub to be able to include , however the build then fails with "undefined reference to `get_unaligned'", because on powerpc get/put_unaligned are defined inside an #ifdef __KERNEL__ block. We probably don't want to define __KERNEL__ for the decompression stub just to avoid an #ifndef in the zlib code.