Re: [PATCH] multi-pack-index: make code -Wunused-parameter clean
On 11/3/2018 10:27 PM, Jeff King wrote:
Show 29 quoted lines
> On Sat, Nov 03, 2018 at 05:49:57PM -0700, Carlo Marcelo Arenas Belón wrote:
>
>> introduced in 662148c435 ("midx: write object offsets", 2018-07-12)
>> but included on all previous versions as well.
>>
>> midx.c:713:54: warning: unused parameter 'nr_objects' [-Wunused-parameter]
>>
>> likely an oversight as the information needed to iterate over is
>> embedded in nr_large_offset
> I've been preparing a series to make the whole code base compile with
> -Wunused-parameter, and I handled this case a bit differently.
>
> -- >8 --
> Subject: [PATCH] midx: double-check large object write loop
>
> The write_midx_large_offsets() function takes an array of object
> entries, the number of entries in the array (nr_objects), and the number
> of entries with large offsets (nr_large_offset). But we never actually
> use nr_objects; instead we keep walking down the array and counting down
> nr_large_offset until we've seen all of the large entries.
>
> This is correct, but we can be a bit more defensive. If there were ever
> a mismatch between nr_large_offset and the actual set of large-offset
> objects, we'd walk off the end of the array.
>
> Since we know the size of the array, we can use nr_objects to make sure
> we don't walk too far.
>
> Signed-off-by: Jeff King <peff@peff.net>Thanks, both, for catching this. I prefer the approach that adds defenses.
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
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> ---
> midx.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/midx.c b/midx.c
> index 4fac0cd08a..ecd583666a 100644
> --- a/midx.c
> +++ b/midx.c
> @@ -712,12 +712,18 @@ static size_t write_midx_object_offsets(struct hashfile *f, int large_offset_nee
> static size_t write_midx_large_offsets(struct hashfile *f, uint32_t nr_large_offset,
> struct pack_midx_entry *objects, uint32_t nr_objects)
> {
> - struct pack_midx_entry *list = objects;
> + struct pack_midx_entry *list = objects, *end = objects + nr_objects;
> size_t written = 0;
>
> while (nr_large_offset) {
> - struct pack_midx_entry *obj = list++;
> - uint64_t offset = obj->offset;
> + struct pack_midx_entry *obj;
> + uint64_t offset;
> +
> + if (list >= end)
> + BUG("too many large-offset objects");
> +
> + obj = list++;
> + offset = obj->offset;
>
> if (!(offset >> 31))
> continue;Derrick Stolee <stolee@gmail.com>