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

[Derrick Stolee <stolee@gmail.com>]

On 8/14/2020 7:10 AM, Jeff King 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).

Good find. The impact of the leak is likely low since we don't create
multiple pattern_list structs per process (with these hashmaps) very
often. The sparse-checkout builtin is likely the only place where
multiple could be instantiated at the same time.

I also double-checked that hashmap_free_entries() handles a NULL
hashmap pointer or uninitialized hashmap, which is what happens
when cone mode is not enabled _or_ the pattern_list corresponds to
something like a .gitignore file.

Thanks,
-Stolee

>  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);
>  
>  	memset(pl, 0, sizeof(*pl));
>  }
>