Re: [PATCH] clear_pattern_list(): clear embedded hashmaps

[Elijah Newren <newren@gmail.com>]

On Mon, Aug 17, 2020 at 9:55 AM Elijah Newren <newren@gmail.com> wrote:
>
> Hi,
>
> On Fri, Aug 14, 2020 at 5:23 AM Jeff King <peff@peff.net> wrote:
> >
> > Commit 96cc8ab531 (sparse-checkout: use hashmaps for cone patterns,
> > 2019-11-21) added some auxiliary hashmaps to the pattern_list struct,
> > but they're leaked when clear_pattern_list() is called.
> >
> > Signed-off-by: Jeff King <peff@peff.net>
> > ---
> > I have no idea how often this leak triggers in practice. I just noticed
> > it while poking at LSan output (which we remain depressingly far
> > from getting a clean run on).
> >
> >  dir.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/dir.c b/dir.c
> > index fe64be30ed..9411b94e9b 100644
> > --- a/dir.c
> > +++ b/dir.c
> > @@ -916,6 +916,8 @@ void clear_pattern_list(struct pattern_list *pl)
> >                 free(pl->patterns[i]);
> >         free(pl->patterns);
> >         free(pl->filebuf);
> > +       hashmap_free_entries(&pl->recursive_hashmap, struct pattern_entry, ent);
> > +       hashmap_free_entries(&pl->parent_hashmap, struct pattern_entry, ent);
>
> This clears up the hash entries, but continues to leak the hash table.
> Since you submitted first, can you fix this to use hashmap_free_()
> instead, as per
> https://lore.kernel.org/git/932741d7598ca2934dbca40f715ba2d3819fcc51.1597561152.git.gitgitgadget@gmail.com/?
>  Then I'll rebase my series on yours and drop my first patch (since
> it'll then be identical).

Nevermind, I got confused once again by the name.
hashmap_free_entries() doesn't mean just free the entries, it means
free what hashmap_free() would plus all the entries, i.e. do what
hashmap_free() *should* *have* *been* defined to do.  Such a confusing
API.  And hashmap_free() really perplexes me -- it seems like a
function that can't possibly be useful; it's sole purpose seems to be
a trap for the unwary.