linux-kernel - Re: [PATCH 10/10] perf script python: Fix string vs byte array resolving

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Date:	Tue, 12 Jul 2016 14:52:45 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Jiri Olsa <jolsa@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 10/10] perf script python: Fix string vs byte array
 resolving

On Tue, Jul 12, 2016 at 08:37:28AM -0400, Steven Rostedt wrote:
> On Tue, 12 Jul 2016 10:11:56 +0200
> Jiri Olsa <jolsa@...hat.com> wrote:
> 
> 
> > ---
> > diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c
> > index 75e9790ebb96..9f810e6c739a 100644
> > --- a/tools/perf/util/scripting-engines/trace-event-python.c
> > +++ b/tools/perf/util/scripting-engines/trace-event-python.c
> > @@ -390,11 +390,13 @@ static int is_printable_array(char *p, unsigned int len)
> >  {
> >  	unsigned int i;
> >  
> > -	for (i = 0; i < len; i++)
> > +	/* Exclude the last zero byte of string.. */
> > +	for (i = 0; i < len - 1; i++)
> >  		if (!isprint(p[i]) && !isspace(p[i]))
> >  			return 0;
> >  
> > -	return 1;
> > +	/* ... and check its presence in the last byte. */
> > +	return p[i] == 0;
> >  }
> >  
> 
> Of course this fails on:
> 
> 	is_printable_array(a, strlen(a));

hum, so string is not passed to trace buffer with 0 at the end?

I'll check the option of passing everything as PyByteArray.
If it's the same for user, we'll have simpler code in here.

> 
> because the last byte wont be 0. What about:
> 
> 	for (i = 0; i < len; i++)
> 		if (!isprint(p[i]) && !isspace(p[i]))
> 			break;
> 
> 	return i == len ||
> 		(i == len - 1 && p[i] == 0);

thanks,
jirka