Re: [PATCH 11/15] midx: use 64-bit multiplication for chunk sizes

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

"Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: Derrick Stolee <dstolee@microsoft.com>
>
> When calculating the sizes of certain chunks, we should use 64-bit
> multiplication always. This allows us to properly predict the chunk
> sizes without risk of overflow.

That's quite an obvious fix, applicable even before this entire
series.  I think we saw quite similar bugfixes in different parts of
the codebase recently.

So far, everything looks good.


> Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
> ---
>  midx.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/midx.c b/midx.c
> index 0548266bea..47f5f60fcd 100644
> --- a/midx.c
> +++ b/midx.c
> @@ -946,12 +946,12 @@ static int write_midx_internal(const char *object_dir, struct multi_pack_index *
>  	chunks[2].write_fn = write_midx_oid_lookup;
>  
>  	chunks[3].id = MIDX_CHUNKID_OBJECTOFFSETS;
> -	chunks[3].size = ctx.entries_nr * MIDX_CHUNK_OFFSET_WIDTH;
> +	chunks[3].size = (uint64_t)ctx.entries_nr * MIDX_CHUNK_OFFSET_WIDTH;
>  	chunks[3].write_fn = write_midx_object_offsets;
>  
>  	if (ctx.large_offsets_needed) {
>  		chunks[4].id = MIDX_CHUNKID_LARGEOFFSETS;
> -		chunks[4].size = ctx.num_large_offsets * MIDX_CHUNK_LARGE_OFFSET_WIDTH;
> +		chunks[4].size = (uint64_t)ctx.num_large_offsets * MIDX_CHUNK_LARGE_OFFSET_WIDTH;
>  		chunks[4].write_fn = write_midx_large_offsets;
>  	}