Re: [PATCH v2 15/17] midx: use 64-bit multiplication for chunk sizes
From: Junio C Hamano <hidden>
Date: 2021-02-05 00:01:25
"Derrick Stolee via GitGitGadget" [off-list ref] writes:
From: Derrick Stolee <redacted> 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 <redacted> --- 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.
quoted hunk
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);