tools lib traceevent: Report better error message on bad function args

When Jiri Olsa was writing a function callback for
scsi_trace_parse_cdb(), he thought that the traceevent library had a
bug in it because he was getting this error:

  Error: expected ')' but read ','
  Error: expected ')' but read ','
  Error: expected ')' but read ','
  Error: expected ')' but read ','

But in truth, he didn't have the write number of arguments for the
function callback, and the error was the library detecting the
discrepancy. A better error message would have prevented the confusion:

  Error: function 'scsi_trace_parse_cdb()' only expects 2 arguments but event scsi_dispatch_cmd_timeout has more
  Error: function 'scsi_trace_parse_cdb()' only expects 2 arguments but event scsi_dispatch_cmd_start has more
  Error: function 'scsi_trace_parse_cdb()' only expects 2 arguments but event scsi_dispatch_cmd_error has more
  Error: function 'scsi_trace_parse_cdb()' only expects 2 arguments but event scsi_dispatch_cmd_done has more

Or

  Error: function 'scsi_trace_parse_cdb()' expects 4 arguments but event scsi_dispatch_cmd_timeout only uses 3
  Error: function 'scsi_trace_parse_cdb()' expects 4 arguments but event scsi_dispatch_cmd_start only uses 3
  Error: function 'scsi_trace_parse_cdb()' expects 4 arguments but event scsi_dispatch_cmd_error only uses 3
  Error: function 'scsi_trace_parse_cdb()' expects 4 arguments but event scsi_dispatch_cmd_done only uses 3

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/n/tip-a4c34w62vl0diitvxb7bt3er@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 18 insertions, 10 deletions

diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
index 9849873265d4..22566c271275 100644
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -2710,7 +2710,6 @@ process_func_handler(struct event_format *event, struct pevent_function_handler
         struct print_arg *farg;
         enum event_type type;
         char *token;
-        const char *test;
         int i;
 
         arg->type = PRINT_FUNC;
@@ -2727,15 +2726,19 @@ process_func_handler(struct event_format *event, struct pevent_function_handler
                 }
 
                 type = process_arg(event, farg, &token);
-                if (i < (func->nr_args - 1))
-                        test = ",";
-                else
-                        test = ")";
-
-                if (test_type_token(type, token, EVENT_DELIM, test)) {
-                        free_arg(farg);
-                        free_token(token);
-                        return EVENT_ERROR;
+                if (i < (func->nr_args - 1)) {
+                        if (type != EVENT_DELIM || strcmp(token, ",") != 0) {
+                                warning("Error: function '%s()' expects %d arguments but event %s only uses %d",
+                                        func->name, func->nr_args,
+                                        event->name, i + 1);
+                                goto err;
+                        }
+                } else {
+                        if (type != EVENT_DELIM || strcmp(token, ")") != 0) {
+                                warning("Error: function '%s()' only expects %d arguments but event %s has more",
+                                        func->name, func->nr_args, event->name);
+                                goto err;
+                        }
                 }
 
                 *next_arg = farg;
@@ -2747,6 +2750,11 @@ process_func_handler(struct event_format *event, struct pevent_function_handler
         *tok = token;
 
         return type;
+
+err:
+        free_arg(farg);
+        free_token(token);
+        return EVENT_ERROR;
 }
 
 static enum event_type