linux-kernel - Re: [PATCH 06/24] perf tools: Add build_id__is

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Date:   Tue, 17 Nov 2020 21:53:59 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Michael Petlan <mpetlan@...hat.com>,
        Song Liu <songliubraving@...com>,
        Stephane Eranian <eranian@...gle.com>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH 06/24] perf tools: Add build_id__is_defined function

On Tue, Nov 17, 2020 at 11:00:37AM -0800, Ian Rogers wrote:
> On Tue, Nov 17, 2020 at 3:01 AM Jiri Olsa <jolsa@...nel.org> wrote:
> 
> > Adding build_id__is_defined helper to check build id
> > is defined and is != zero build id.
> >
> > Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> > ---
> >  tools/perf/util/build-id.c | 7 +++++++
> >  tools/perf/util/build-id.h | 1 +
> >  2 files changed, 8 insertions(+)
> >
> > diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
> > index 6b410c3d52dc..7d9ecc37849c 100644
> > --- a/tools/perf/util/build-id.c
> > +++ b/tools/perf/util/build-id.c
> > @@ -912,3 +912,10 @@ void build_id__init(struct build_id *bid, const u8
> > *data, size_t size)
> >         memcpy(bid->data, data, size);
> >         bid->size = size;
> >  }
> > +
> > +bool build_id__is_defined(const struct build_id *bid)
> > +{
> > +       static u8 zero[BUILD_ID_SIZE];
> > +
> > +       return bid && bid->size ? memcmp(bid->data, &zero, bid->size) :
> > false;
> >
> 
> Fwiw, I find this method to test for zero a little hard to parse - I'm

heh, it's controversial one, Namhyung commented
on this one in previous version, so I changed it ;-)
  https://lore.kernel.org/lkml/CAM9d7cjjGjTN8sDgLZ1PoQZ-sUXWjnVaNdyOVE1yHxq46PrPkw@mail.gmail.com/


> failing as a C programmer :-) Nit, should zero be const?

right, should be const, will change

thanks,
jirka