[PATCH] perf stat: Fail on extra comma while parsing events

[Jiri Olsa <jolsa@kernel.org>]

Ian reported that we allow to parse following:

  $ perf stat -e ,cycles true

which is wrong and we should fail, like we do with this fix:

  $ perf stat -e ,cycles true
  event syntax error: ',cycles'
                        \___ parser error

The reason is that we don't have rule for ',' in 'event'
start condition and it's matched and accepted by default
rule.

Adding scanner debug support (that Ian already added for
expr code), which was really useful for finding this. It's
enabled together with bison debug via 'make PARSER_DEBUG=1'.

Reported-by: Ian Rogers <irogers@google.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 tools/perf/util/parse-events.c | 1 +
 tools/perf/util/parse-events.l | 4 +++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index e37a6a3e6217..d251c8a778b8 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -2014,6 +2014,7 @@ static int parse_events__scanner(const char *str, void *parse_state, int start_t
 
 #ifdef PARSER_DEBUG
 	parse_events_debug = 1;
+	parse_events_set_debug(1, scanner);
 #endif
 	ret = parse_events_parse(parse_state, scanner);
 
diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
index c589fc42f058..394132254447 100644
--- a/tools/perf/util/parse-events.l
+++ b/tools/perf/util/parse-events.l
@@ -252,7 +252,9 @@ modifier_bp	[rwx]{1,3}
 			BEGIN(INITIAL);
 			REWIND(0);
 		}
-
+,		{
+			return ',';
+		}
 }
 
 <array>{
-- 
2.25.4