multi-pack-index: verify object offsets

The 'git multi-pack-index verify' command must verify the object
offsets stored in the multi-pack-index are correct. There are two
ways the offset chunk can be incorrect: the pack-int-id and the
object offset.

Replace the BUG() statement with a die() statement, now that we
may hit a bad pack-int-id during a 'verify' command on a corrupt
multi-pack-index, and it is covered by a test.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 28 insertions, 1 deletions

diff --git a/midx.c b/midx.c
index db9c49bb2b..ef4a6969df 100644
--- a/midx.c
+++ b/midx.c
@@ -197,7 +197,8 @@ int prepare_midx_pack(struct multi_pack_index *m, uint32_t pack_int_id)
 	struct strbuf pack_name = STRBUF_INIT;
 
 	if (pack_int_id >= m->num_packs)
-		BUG("bad pack-int-id");
+		die(_("bad pack-int-id: %u (%u total packs"),
+		    pack_int_id, m->num_packs);
 
 	if (m->packs[pack_int_id])
 		return 0;
@@ -970,5 +971,31 @@ int verify_midx_file(const char *object_dir)
 				    i, oid_to_hex(&oid1), oid_to_hex(&oid2), i + 1);
 	}
 
+	for (i = 0; i < m->num_objects; i++) {
+		struct object_id oid;
+		struct pack_entry e;
+		off_t m_offset, p_offset;
+
+		nth_midxed_object_oid(&oid, m, i);
+		if (!fill_midx_entry(&oid, &e, m)) {
+			midx_report(_("failed to load pack entry for oid[%d] = %s"),
+				    i, oid_to_hex(&oid));
+			continue;
+		}
+
+		if (open_pack_index(e.p)) {
+			midx_report(_("failed to load pack-index for packfile %s"),
+				    e.p->pack_name);
+			break;
+		}
+
+		m_offset = e.offset;
+		p_offset = find_pack_entry_one(oid.hash, e.p);
+
+		if (m_offset != p_offset)
+			midx_report(_("incorrect object offset for oid[%d] = %s: %"PRIx64" != %"PRIx64),
+				    i, oid_to_hex(&oid), m_offset, p_offset);
+	}
+
 	return verify_midx_error;
 }