Re: [PATCH v2 15/17] midx: use 64-bit multiplication for chunk sizes
"Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com> writes:
Show 10 quoted lines
> 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.
>
> Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
> ---
> midx.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
This one I find somewhat questionable for multiple reasons.
* the fourth parameter of add_chunk() is of size_t, not uint64_t;
shouldn't the multiplication be done in type size_t instead?
* these mutiplications were introduced in "midx: use chunk-format
API in write_midx_internal()"; that step should use the
arithmetic with cast (if necessary) from the start, no?
* There is "ctx.entries_nr * MIDX_CHUNKID_OFFSET_WIDTH" passed to
add_chunk(), in the post-context of the first hunk. Shouldn't
that be covered as well? I didn't grep for all uses of
add_chunk(), but I wouldn't be surprised if this patch missed
some of the calls that need the same treatment.
Show 22 quoted lines
> diff --git a/midx.c b/midx.c
> index e94dcd34b7f..a365dac6bbc 100644
> --- a/midx.c
> +++ b/midx.c
> @@ -913,7 +913,7 @@ static int write_midx_internal(const char *object_dir, struct multi_pack_index *
> add_chunk(cf, MIDX_CHUNKID_OIDFANOUT,
> write_midx_oid_fanout, MIDX_CHUNK_FANOUT_SIZE);
> add_chunk(cf, MIDX_CHUNKID_OIDLOOKUP,
> - write_midx_oid_lookup, ctx.entries_nr * the_hash_algo->rawsz);
> + write_midx_oid_lookup, (uint64_t)ctx.entries_nr * the_hash_algo->rawsz);
> add_chunk(cf, MIDX_CHUNKID_OBJECTOFFSETS,
> write_midx_object_offsets,
> ctx.entries_nr * MIDX_CHUNK_OFFSET_WIDTH);
> @@ -921,7 +921,7 @@ static int write_midx_internal(const char *object_dir, struct multi_pack_index *
> if (ctx.large_offsets_needed)
> add_chunk(cf, MIDX_CHUNKID_LARGEOFFSETS,
> write_midx_large_offsets,
> - ctx.num_large_offsets * MIDX_CHUNK_LARGE_OFFSET_WIDTH);
> + (uint64_t)ctx.num_large_offsets * MIDX_CHUNK_LARGE_OFFSET_WIDTH);
>
> write_midx_header(f, get_num_chunks(cf), ctx.nr - dropped_packs);
> write_chunkfile(cf, &ctx);
Junio C Hamano <gitster@pobox.com>