From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S966056AbdEWHgD (ORCPT <rfc822;w@1wt.eu>);
        Tue, 23 May 2017 03:36:03 -0400
Received: from bombadil.infradead.org ([65.50.211.133]:59895 "EHLO
        bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S933857AbdEWHgB (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 23 May 2017 03:36:01 -0400
Date: Tue, 23 May 2017 00:36:01 -0700
From: Christoph Hellwig <hch@infradead.org>
To: Matthias Kaehlcke <mka@chromium.org>
Cc: linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] zlib: Put get_unaligned16() inside #ifdef block
Message-ID: <20170523073601.GA29525@infradead.org>
References: <20170522211326.66973-1-mka@chromium.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20170522211326.66973-1-mka@chromium.org>
User-Agent: Mutt/1.8.0 (2017-02-23)
X-SRS-Rewrite: SMTP reverse-path rewritten from <hch@infradead.org> by bombadil.infradead.org. See http://www.infradead.org/rpr.html
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

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 <mka@chromium.org>
> ---
> 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 <linux/compiler.h> 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.