perf parse: Fix potential memory leak when handling tracepoint errors

An error may be in place when tracepoint_error is called, use
parse_events__handle_error to avoid a memory leak and to capture the
first and last error. Error detected by LLVM's libFuzzer using the
following event:

$ perf stat -e 'msr/event/,f:e'
event syntax error: 'msr/event/,f:e'
                     \___ can't access trace events

Error:  No permissions to read /sys/kernel/debug/tracing/events/f/e
Hint:   Try 'sudo mount -o remount,mode=755 /sys/kernel/debug/tracing/'

Initial error:
event syntax error: 'msr/event/,f:e'
                                \___ no value assigned for term
Run 'perf list' for a list of valid events

 Usage: perf stat [<options>] [<command>]

    -e, --event <event>   event selector. use 'perf list' to list available events
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: clang-built-linux@googlegroups.com
Link: http://lore.kernel.org/lkml/20191120180925.21787-1-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/parse-events.c

@@ -511,6 +511,7 @@ int parse_events_add_cache(struct list_head *list, int *idx,
 static void tracepoint_error(struct parse_events_error *e, int err,
 			     const char *sys, const char *name)
 {
+	const char *str;
 	char help[BUFSIZ];
 
 	if (!e)
@@ -524,18 +525,18 @@ static void tracepoint_error(struct parse_events_error *e, int err,
 
 	switch (err) {
 	case EACCES:
-		e->str = strdup("can't access trace events");
+		str = "can't access trace events";
 		break;
 	case ENOENT:
-		e->str = strdup("unknown tracepoint");
+		str = "unknown tracepoint";
 		break;
 	default:
-		e->str = strdup("failed to add tracepoint");
+		str = "failed to add tracepoint";
 		break;
 	}
 
 	tracing_path__strerror_open_tp(err, help, sizeof(help), sys, name);
-	e->help = strdup(help);
+	parse_events__handle_error(e, 0, strdup(str), strdup(help));
 }
 
 static int add_tracepoint(struct list_head *list, int *idx,