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Date:   Wed, 13 Sep 2023 21:42:32 -0700
Message-Id: <20230914044233.1550195-1-irogers@google.com>
Mime-Version: 1.0
Subject: [PATCH v1] perf symbol: Avoid an undefined behavior warning
From:   Ian Rogers <irogers@google.com>
To:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Ian Rogers <irogers@google.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        James Clark <james.clark@arm.com>,
        linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
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Precedence: bulk

The node (nd) may be NULL and pointer arithmetic on NULL is undefined
behavior. Move the computation of next below the NULL check on the
node.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/symbol.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 3f36675b7c8f..5b54d2639df4 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -202,11 +202,10 @@ void symbols__fixup_duplicate(struct rb_root_cached *symbols)
 		curr = rb_entry(nd, struct symbol, rb_node);
 again:
 		nd = rb_next(&curr->rb_node);
-		next = rb_entry(nd, struct symbol, rb_node);
-
 		if (!nd)
 			break;
 
+		next = rb_entry(nd, struct symbol, rb_node);
 		if (curr->start != next->start)
 			continue;
 
-- 
2.42.0.459.ge4e396fd5e-goog