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Date: Tue, 10 Dec 2013 09:01:43 -0300
From: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
To: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org, Adrian Hunter <adrian.hunter@intel.com>,
        Andi Kleen <ak@linux.intel.com>, Ben Cheng <bccheng@google.com>,
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        Mike Galbraith <efault@gmx.de>, Namhyung Kim <namhyung.kim@lge.com>,
        Paul Mackerras <paulus@samba.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Stephane Eranian <eranian@google.com>,
        Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [GIT PULL 00/21] perf/core improvements and fixes
Message-ID: <20131210120143.GJ8098@ghostprotocols.net>
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Em Tue, Dec 10, 2013 at 12:47:57PM +0100, Ingo Molnar escreveu:
> * Arnaldo Carvalho de Melo <acme@ghostprotocols.net> wrote:
> > Em Tue, Dec 10, 2013 at 12:12:29PM +0100, Ingo Molnar escreveu:
> > > Hm, I've unpulled it because 'perf top' crashes on exit, in 
> > > dso__delete():

> > 495		if (dso->sname_alloc)
> > 496			free((char *)dso->short_name)

> Btw., instead of trusting flags I'd argue that using the pointer as a 
> flag and clearing the pointer too is a much more robust freeing 
> pattern in general:

> 		if (dso->short_name) {
> 			free(dso->short_name);
> 			dso->short_name = NULL;
> 		}
> 
> or so ...

This is not an unusual idiom, if you look at tools/perf/util/ev{list,sel}.c,
for instance, you'll see it in many destructors.

In this case there is a micro optimization where sometimes the shortname
is just a pointer to the tail part of the long name, hence the flag.

- Arnaldo