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

[Steven Rostedt <rostedt@goodmis.org>]

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;
> 
> 
> 
> 
> > +	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;
> > +}