[PATCH 0/5] midx-write: fix segfault and do several cleanups

I was motivated to start looking closely at midx-write.c due to multiple users reporting Git crashes in their background maintenance, specifically during git multi-pack-index repack calls. I was eventually able to reproduce it in git multi-pack-index expire as well.

Patch 1 is the only change we need to fix this bug. It includes a test case that will fail under --stress with SANITIZE=address. It requires creating many packfiles (50 was not enough, but 100 is enough). As far as I can tell, this bug has existed since Git 2.47.0 in October 2024, but I started hearing reports of this from users in July 2025 (and took a while to get a dump/repro).

The remaining patches are cleanups based on my careful rereading of midx-write.c. There are some issues about error handling that needed some cleanup as well as a removal of the DISABLE_SIGN_COMPARE_WARNINGS macro.

Thanks, -Stolee

Derrick Stolee (5):
  midx-write: only load initialized packs
  midx-write: put failing response value back
  midx-write: use cleanup when incremental midx fails
  midx-write: use uint32_t for preferred_pack_idx
  midx-write: reenable signed comparison errors

 midx-write.c                | 118 ++++++++++++++++++------------------
 t/t5319-multi-pack-index.sh |  17 ++++++
 2 files changed, 75 insertions(+), 60 deletions(-)

base-commit: c44beea485f0f2feaf460e2ac87fdd5608d63cf0
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1965%2Fderrickstolee%2Fmidx-write-cleanup-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1965/derrickstolee/midx-write-cleanup-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1965