tools lib traceevent: Make sure that arg->op.right is set properly

When process_op failed, @arg will be freed on a caller with type of
PRINT_OP.  Thus free_arg() will try to free ->op.right field which can
have stale value if something bad happens in the middle.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1348037924-17568-3-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/lib/traceevent/event-parse.c

@@ -1719,6 +1719,7 @@ process_op(struct event_format *event, struct print_arg *arg, char **tok)
 		arg->op.left = left;
 		arg->op.prio = 0;
 
+		/* it will set arg->op.right */
 		type = process_cond(event, arg, tok);
 
 	} else if (strcmp(token, ">>") == 0 ||
@@ -1745,6 +1746,7 @@ process_op(struct event_format *event, struct print_arg *arg, char **tok)
 		arg->type = PRINT_OP;
 		arg->op.op = token;
 		arg->op.left = left;
+		arg->op.right = NULL;
 
 		if (set_op_prio(arg) == -1) {
 			event->flags |= EVENT_FL_FAILED;
@@ -1792,6 +1794,7 @@ process_op(struct event_format *event, struct print_arg *arg, char **tok)
 
 		arg->op.prio = 0;
 
+		/* it will set arg->op.right */
 		type = process_array(event, arg, tok);
 
 	} else {