linux-kernel - Re: tools lib traceevent: Report better error message on bad function args

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Date:	Tue, 19 Nov 2013 11:23:56 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Jiri Olsa <jolsa@...hat.com>, Ingo Molnar <mingo@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: tools lib traceevent: Report better error message on bad function args

Hi Steven,

On Mon, 18 Nov 2013 19:11:31 -0500, Steven Rostedt wrote:
> 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@...dmis.org>
>
> diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
> index 0362d57..f7aab3d 100644
> --- a/tools/lib/traceevent/event-parse.c
> +++ b/tools/lib/traceevent/event-parse.c
> @@ -2691,7 +2691,6 @@ 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;
> @@ -2708,15 +2707,19 @@ 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);
> +				return EVENT_ERROR;
> +			}
> +		} 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);
> +				return EVENT_ERROR;

It seems that you missed to free farg and token in error paths.

Thanks,
Namhyung


> +			}
>  		}
>  
>  		*next_arg = farg;
--
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