Re: What's cooking in git.git (Sep 2016, #03; Fri, 9)

[Junio C Hamano <gitster@pobox.com>]

Jeff King <peff@peff.net> writes:

> I happened to notice today that this topic needs a minor tweak:
>
> -- >8 --
> Subject: [PATCH] add_delta_base_cache: use list_for_each_safe
>
> We may remove elements from the list while we are iterating,
> which requires using a second temporary pointer. Otherwise
> stepping to the next element of the list might involve
> looking at freed memory (which generally works in practice,
> as we _just_ freed it, but of course is wrong to rely on;
> valgrind notices it).

I failed to notice it, too.  Thanks.

> Signed-off-by: Jeff King <peff@peff.net>
> ---
>  sha1_file.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/sha1_file.c b/sha1_file.c
> index a57b71d..132c861 100644
> --- a/sha1_file.c
> +++ b/sha1_file.c
> @@ -2187,11 +2187,11 @@ static void add_delta_base_cache(struct packed_git *p, off_t base_offset,
>  	void *base, unsigned long base_size, enum object_type type)
>  {
>  	struct delta_base_cache_entry *ent = xmalloc(sizeof(*ent));
> -	struct list_head *lru;
> +	struct list_head *lru, *tmp;
>  
>  	delta_base_cached += base_size;
>  
> -	list_for_each(lru, &delta_base_cache_lru) {
> +	list_for_each_safe(lru, tmp, &delta_base_cache_lru) {
>  		struct delta_base_cache_entry *f =
>  			list_entry(lru, struct delta_base_cache_entry, lru);
>  		if (delta_base_cached <= delta_base_cache_limit)