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 S1754104AbbEKOlS (ORCPT <rfc822;w@1wt.eu>);
	Mon, 11 May 2015 10:41:18 -0400
Received: from mail.kernel.org ([198.145.29.136]:44817 "EHLO mail.kernel.org"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1751825AbbEKOlO (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Mon, 11 May 2015 10:41:14 -0400
Date: Mon, 11 May 2015 11:41:10 -0300
From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Namhyung Kim <namhyung@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Jiri Olsa <jolsa@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
        David Ahern <dsahern@gmail.com>, Joonsoo Kim <js1304@gmail.com>,
        Minchan Kim <minchan@kernel.org>, Pekka Enberg <penberg@kernel.org>,
        linux-mm@kvack.org
Subject: Re: [PATCH 4/6] perf kmem: Print gfp flags in human readable string
Message-ID: <20150511144110.GR28183@kernel.org>
References: <1429592107-1807-1-git-send-email-namhyung@kernel.org>
 <1429592107-1807-5-git-send-email-namhyung@kernel.org>
 <20150511143536.GP28183@kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20150511143536.GP28183@kernel.org>
X-Url: http://acmel.wordpress.com
User-Agent: Mutt/1.5.23 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Em Mon, May 11, 2015 at 11:35:36AM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Tue, Apr 21, 2015 at 01:55:05PM +0900, Namhyung Kim escreveu:
> > Save libtraceevent output and print it in the header.
> 
> <SNIP>
> 
> > +static int parse_gfp_flags(struct perf_evsel *evsel, struct perf_sample *sample,
> > +			   unsigned int gfp_flags)
> > +{
> > +	char *str, *pos;

> > +	str = strtok_r(seq.buffer, " ", &pos);
> 
> builtin-kmem.c:743:427: error: ‘pos’ may be used uninitialized in this
> function [-Werror=maybe-uninitialized]
>     new->human_readable = strdup(str + 10);
>                                                                                                                                                                                                                                                                                                                                                                                                                                            ^
> builtin-kmem.c:716:14: note: ‘pos’ was declared here
>   char *str, *pos;
>               ^

Emphasis on the "may", as according to strtok_r your code is ok, its
just the compiler that needs to be told that no, it is not being
accessed uninitialized:

<quote man strtok>
       On the first call to strtok_r(), str should point to the string
to be parsed, and the value of saveptr is ignored.  In subsequent calls,
str should be NULL, and saveptr should be unchanged since the previous
call.
</>

So just setting it to NULL is enough.

- Arnaldo