perf test demangle-java: Don't segv if demangling fails

The buffer returned by dso__demangle_sym() may be NULL, don't segv in
strcmp if this happens.

Currently this happens for NO_LIBELF=1 builds.

Signed-off-by: Ian Rogers <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alex Gaynor <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Alice Ryhl <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Andreas Hindborg <[email protected]>
Cc: Benno Lossin <[email protected]>
Cc: Björn Roy Baron <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Danilo Krummrich <[email protected]>
Cc: Dmitriy Vyukov <[email protected]>
Cc: Gary Guo <[email protected]>
Cc: Howard Chu <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: James Clark <[email protected]>
Cc: Jiapeng Chong <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Miguel Ojeda <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephen Brennan <[email protected]>
Cc: Trevor Gross <[email protected]>
Cc: Weilin Wang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: captain5050

tools/perf/tests/demangle-java-test.c

@@ -30,6 +30,11 @@ static int test__demangle_java(struct test_suite *test __maybe_unused, int subte
 
 	for (i = 0; i < ARRAY_SIZE(test_cases); i++) {
 		buf = dso__demangle_sym(/*dso=*/NULL, /*kmodule=*/0, test_cases[i].mangled);
+		if (!buf) {
+			pr_debug("FAILED to demangle: \"%s\"\n \"%s\"\n", test_cases[i].mangled,
+				 test_cases[i].demangled);
+			continue;
+		}
 		if (strcmp(buf, test_cases[i].demangled)) {
 			pr_debug("FAILED: %s: %s != %s\n", test_cases[i].mangled,
 				 buf, test_cases[i].demangled);