linux-kernel - Re: [PATCH 02/14] tools lib traceevent: Get rid of die in add_filter

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Date:	Tue, 10 Dec 2013 09:32:52 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Namhyung Kim <namhyung.kim@....com>
Subject: Re: [PATCH 02/14] tools lib traceevent: Get rid of die in add_filter_type()

On Mon, 9 Dec 2013 11:44:37 +0100, Jiri Olsa wrote:
> On Mon, Dec 09, 2013 at 02:33:59PM +0900, Namhyung Kim wrote:
>> The realloc() should check return value and not to overwrite previous
>> pointer in case of error.
>> 
>> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
>> ---
>>  tools/lib/traceevent/parse-filter.c | 21 ++++++++++++++++-----
>>  1 file changed, 16 insertions(+), 5 deletions(-)
>> 
>> diff --git a/tools/lib/traceevent/parse-filter.c b/tools/lib/traceevent/parse-filter.c
>> index 0fc905c230ad..d9c239933992 100644
>> --- a/tools/lib/traceevent/parse-filter.c
>> +++ b/tools/lib/traceevent/parse-filter.c
>> @@ -161,11 +161,13 @@ add_filter_type(struct event_filter *filter, int id)
>>  	if (filter_type)
>>  		return filter_type;
>>  
>> -	filter->event_filters =	realloc(filter->event_filters,
>> -					sizeof(*filter->event_filters) *
>> -					(filter->filters + 1));
>> -	if (!filter->event_filters)
>> -		die("Could not allocate filter");
>> +	filter_type = realloc(filter->event_filters,
>> +			      sizeof(*filter->event_filters) *
>> +			      (filter->filters + 1));
>> +	if (!filter_type)
>> +		return NULL;
>> +
>> +	filter->event_filters = filter_type;
>>  
>>  	for (i = 0; i < filter->filters; i++) {
>>  		if (filter->event_filters[i].event_id > id)
>> @@ -1164,6 +1166,12 @@ static int filter_event(struct event_filter *filter,
>>  	}
>>  
>>  	filter_type = add_filter_type(filter, event->id);
>> +	if (filter_type == NULL) {
>> +		show_error(error_str, "failed to add a new filter: %s",
>> +			   filter_str ? filter_str : "true");
>> +		return -1;
>
> so your key for using show_error in case of error is if it's
> used already in the error path in the function.. right?

Right.  In fact, it might look better if copy_filter_type() or
pevent_filter_copy() pass error_str too.  But the pevent_filter_
copy() looks like an user API so I was not sure I can change the
signature.  Also user can see its return value anyway and it's
relatively simple function so might not care about the detail..

Thanks,
Namhyung

>
>> +	}
>> +
>>  	if (filter_type->filter)
>>  		free_arg(filter_type->filter);
>>  	filter_type->filter = arg;
>> @@ -1395,6 +1403,9 @@ static int copy_filter_type(struct event_filter *filter,
>>  			arg->boolean.value = 0;
>>  
>>  		filter_type = add_filter_type(filter, event->id);
>> +		if (filter_type == NULL)
>> +			return -1;
>> +
>>  		filter_type->filter = arg;
>>  
>>  		free(str);
>> -- 
>> 1.7.11.7
>> 
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