Re: [PATCH v4 1/7] libtracefs: Implement tracefs_instances()

["Yordan Karadzhov (VMware)" <y.karadz@gmail.com>]

On 2.07.21 г. 14:33, Steven Rostedt wrote:
> On Fri, 2 Jul 2021 14:10:46 +0300
> "Yordan Karadzhov (VMware)" <y.karadz@gmail.com> wrote:
> 
>>> +static int build_list(const char *name, void *data)
>>> +{
>>> +	struct instance_list *list = data;
>>> +	char **instances;
>>> +	int ret = -1;
>>> +
>>> +	if (!match(name, list->re))
>>> +		return 0;
>>> +
>>> +	instances = realloc(list->list, list->size + 2);
>>> +	if (!instances)
>>> +		goto out;
>>> +
>>> +	list->list = instances;
>> Hi Steven,
>>
>> I am not sure what was your original intention here, but this doesn't
>> seem to work properly. Maybe we need something like this:
>>
>> 	int size =  sizeof(*instances) * (list->size + 2);
>> 	instances = realloc(list->list, size);
> 
> Bah, that's what I get for trying to "multitask" while coding :-p
> That was suppose to be:
> 
> 	instances = realloc(list->list, sizeof(*instances) * (list->size + 2);
> 
> as you stated, but I'll keep it one line.
> 
>> 	if (!instances)
>> 		goto out;
>>
>> 	instances[list->size + 1] = NULL;

but you still need to make sure it is NULL terminated.
Y.

>>
>>
>>
>>
>>> +	list->list[list->size] = strdup(name);
>>> +	if (!list->list[list->size])
>>> +		goto out;
>>> +
>>> +	list->size++;
>>> +	ret = 0;
>>> +
>>> + out:
>>> +	list->failed = ret;
>>> +	return ret;
>>> +}
>>> +
>>> +/**
>>> + * tracefs_instances - return a list of instance names
>>> + * @regex: A regex of instances to filter on (NULL to match all)
>>> + *
>>> + * Returns a list of names of existing instances, that must be
>>> + * freed with tracefs_list_free(). Note, if there are no matches
>>> + * then an empty list will be returned (not NULL).
>>> + * NULL on error.
>>> + */
>>> +char **tracefs_instances(const char *regex)
>>> +{
>>> +	struct instance_list list = { .re = NULL, .list = NULL };
>>> +	regex_t re;
>>> +	int ret;
>>> +
>>> +	if (regex) {
>>> +		ret = regcomp(&re, regex, REG_ICASE|REG_NOSUB);
>>> +		if (ret < 0)
>>> +			return NULL;
>>> +		list.re = &re;
>>> +	}
>>> +
>>> +	ret = tracefs_instances_walk(build_list, &list);
>>> +	if (ret < 0 || list.failed) {
>>> +		tracefs_list_free(list.list);
>>> +		list.list = NULL;
>>> +	} else {
>>> +		if (!list.list) {
>>> +			/* No matches should produce an empty list */
>>> +			list.list = malloc(sizeof(*list.list));
>>> +			if (list.list)
>>> +				list.list[0] = NULL;
>>> +		}
>>
>> Or you can just do:
>> 				return calloc(1, sizeof(*list.list));
> 
> Which I do in tracefs_get_probes(), must have missed this one.
> 
> Will update, thanks for the review.
> 
> 
> -- Steve
> 
> 
>>
>> Thanks!
>> Yordan
>>
>>> +	}
>>> +	return list.list;
>>> +}