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SubjectRe: [PATCH] perf tools: Don't write to evsel if parser doesn't collect evsel
On Wed, Sep 02, 2015 at 08:05:54PM +0800, pi3orama wrote:

SNIP

> >>> perf_evlist__splice_list_tail(evlist, &data.list, entries);
> >>> evlist->nr_groups += data.nr_groups;
> >>> - last = perf_evlist__last(evlist);
> >>> - last->cmdline_group_boundary = true;
> >>> return 0;
> >>> }
> >>> @@ -1252,7 +1262,13 @@ foreach_evsel_in_last_glob(struct perf_evlist *evlist,
> >>> struct perf_evsel *last = NULL;
> >>> int err;
> >>> - if (evlist->nr_entries > 0)
> >>> + /*
> >>> + * Don't return when list_empty, give func a chance to report
> >>> + * error when it found last == NULL.
> >>> + *
> >>> + * So no need to WARN here, let *func do this.
> >>> + */
> >>> + if (!list_empty(&evlist->entries))
> >
> > why is it better than to check evlist->nr_entries?
> > evlist->nr_entries is equivalent to !list_empty(&evlist->entries) in here, right?
> >
>
> By checking list we won't rely on the assumption that nr_entries reflects the
> actual number of elements in that list, makes the logic of this code more compact.
> Don't you think so?
>
> At this point they are equivalent, but the whole patch is preventive action.

ok, fair enough ;-)

Acked-by: Jiri Olsa <jolsa@kernel.org>

thanks,
jirka


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