Re: [RFC PATCH 4/5] pack-objects: avoid reading uninitalized data

> In the main loop of find_deltas, we do:
> 
>   struct object_entry *entry = *list++;
>   ...
>   if (!*list_size)
> 	  ...
> 	  break
> 
> Because we look at and increment *list _before_ the check of
> list_size, in the very last iteration of the loop we will
> look at uninitialized data, and increment the pointer beyond
> one past the end of the allocated space. Since we don't
> actually do anything with the data until after the check,
> this is not a problem in practice.
> 
> But since it technically violates the C standard, and
> because it provokes a spurious valgrind warning, let's just
> move the initialization of entry to a safe place.
> 
> This fixes valgrind errors in t5300, t5301, t5302, t303, and
> t9400.
> 
> Signed-off-by: Jeff King <peff@peff.net>

> ---
>  builtin-pack-objects.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c
> index 59c30d1..15b80db 100644
> --- a/builtin-pack-objects.c
> +++ b/builtin-pack-objects.c
> @@ -1375,7 +1375,7 @@ static void find_deltas(struct object_entry **list, unsigned *list_size,
>  	array = xcalloc(window, sizeof(struct unpacked));
>  
>  	for (;;) {
> -		struct object_entry *entry = *list++;
> +		struct object_entry *entry;
>  		struct unpacked *n = array + idx;
>  		int j, max_depth, best_base = -1;
>  
> @@ -1384,6 +1384,7 @@ static void find_deltas(struct object_entry **list, unsigned *list_size,
>  			progress_unlock();
>  			break;
>  		}