perf stat: Avoid uninitialized use of perf_stat_config

perf_event__read_stat_config will assign values based on number of
tags and tag values. Initialize the structs to zero before they are
assigned so that no uninitialized values can be seen.

This potential error was reported by GCC with LTO enabled.
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Carsten Haitzler <carsten.haitzler@arm.com>
Cc: Fangrui Song <maskray@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Tom Rix <trix@redhat.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Cc: Yang Jihong <yangjihong1@huawei.com>
Cc: bpf@vger.kernel.org
Cc: llvm@lists.linux.dev
Link: https://lore.kernel.org/r/20230724201247.748146-2-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/stat.c

@@ -27,7 +27,7 @@ static int process_stat_config_event(struct perf_tool *tool __maybe_unused,
 				     struct machine *machine __maybe_unused)
 {
 	struct perf_record_stat_config *config = &event->stat_config;
-	struct perf_stat_config stat_config;
+	struct perf_stat_config stat_config = {};
 
 #define HAS(term, val) \
 	has_term(config, PERF_STAT_CONFIG_TERM__##term, val)

tools/perf/util/stat.c

@@ -729,7 +729,7 @@ size_t perf_event__fprintf_stat_round(union perf_event *event, FILE *fp)
 
 size_t perf_event__fprintf_stat_config(union perf_event *event, FILE *fp)
 {
-	struct perf_stat_config sc;
+	struct perf_stat_config sc = {};
 	size_t ret;
 
 	perf_event__read_stat_config(&sc, &event->stat_config);