linux-kernel - Re: [PATCH 4/6] perf kmem: Print gfp flags in human readable string

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Message-ID: <20150511152647.GB12220@danjae.kornet>
Date:	Tue, 12 May 2015 00:26:47 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Jiri Olsa <jolsa@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Joonsoo Kim <js1304@...il.com>,
	Minchan Kim <minchan@...nel.org>,
	Pekka Enberg <penberg@...nel.org>, linux-mm@...ck.org
Subject: Re: [PATCH 4/6] perf kmem: Print gfp flags in human readable string

On Mon, May 11, 2015 at 11:41:10AM -0300, Arnaldo Carvalho de Melo wrote:
> 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.

Agreed.

Thanks for fixing this,
Namhyung
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