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

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

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
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