linux-kernel - Re: [PATCH v2] perf data: Add JSON export

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Message-ID: <YIgJY5jejgvTWqmR@kernel.org>
Date:   Tue, 27 Apr 2021 09:53:55 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Nicholas Fraser <nfraser@...eweavers.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Changbin Du <changbin.du@...el.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Tan Xiaojun <tanxiaojun@...wei.com>,
        Jin Yao <yao.jin@...ux.intel.com>,
        linux-kernel@...r.kernel.org,
        Ulrich Czekalla <uczekalla@...eweavers.com>
Subject: Re: [PATCH v2] perf data: Add JSON export

Em Mon, Apr 26, 2021 at 06:24:29PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Mon, Apr 26, 2021 at 05:25:58PM -0300, Arnaldo Carvalho de Melo escreveu:
> > Em Mon, Apr 26, 2021 at 10:47:16AM -0400, Nicholas Fraser escreveu:
> > > This adds a feature to export perf data to JSON.
> > > 
> > > The resolved symbols are exported into the JSON so that external tools
> > > don't need to load the dsos themselves (or even have access to them at
> > > all.) This makes it easy to load and analyze perf data with standalone
> > > tools where direct perf or libbabeltrace integration is impractical.
> > > 
> > > The exporter uses a minimal inline JSON encoding without any external
> > > dependencies. Currently it only outputs some headers and sample metadata
> > > but it's easily extensible.
> > > 
> > > Use it like this:
> > > 
> > > perf data convert --to-json out.json
> 
> One more, clang complains:
> 
>    7    50.92 alpine:3.10                   : FAIL gcc version 8.3.0 (Alpine 8.3.0)
>     util/data-convert-json.c:126:32: error: address of array 'al->sym->name' will always evaluate to 'true' [-Werror,-Wpointer-bool-conversion]
>             if (al && al->sym && al->sym->name && strlen(al->sym->name) > 0) {
>                               ~~ ~~~~~~~~~^~~~
>     1 error generated.
>     make[3]: *** [/git/perf-5.12.0/tools/build/Makefile.build:139: util] Error 2

So the fix is the one below, applied and tested, thanks.

- Arnaldo

diff --git a/tools/perf/util/data-convert-json.c b/tools/perf/util/data-convert-json.c
index f24593d57f80be1b..355cd1948bdf006a 100644
--- a/tools/perf/util/data-convert-json.c
+++ b/tools/perf/util/data-convert-json.c
@@ -123,7 +123,7 @@ static void output_sample_callchain_entry(struct perf_tool *tool,
 	output_json_format(out, false, 4, "{");
 	output_json_key_format(out, false, 5, "ip", "\"0x%" PRIx64 "\"", ip);
 
-	if (al && al->sym && al->sym->name && strlen(al->sym->name) > 0) {
+	if (al && al->sym && al->sym->namelen) {
 		fputc(',', out);
 		output_json_key_string(out, false, 5, "symbol", al->sym->name);