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Re: [PATCH 4/4] pack-check: fix verification of large objects

From
Jeff King <peff@peff.net>
Date
Feb 23, 2026, 12:58 UTC
Message-ID
<20260223125843.GA215671@coredump.intra.peff.net>
In-Reply-To
<aZw6W_BHoYiC9RYl@pks.im>
On Mon, Feb 23, 2026 at 12:30:35PM +0100, Patrick Steinhardt wrote:
Show 17 quoted lines
> > A more concrete test would probably be something like:
> > 
> >    1. Two packs, $X and $Y, both contain the same object.
> > 
> >    2. The object is corrupt in $X but not in $Y.
> > 
> >    3. Running fsck detects that one copy is corrupt but the other is
> >       not.
> > 
> > Right now it may or may not fail depending on the ordering of the packs
> > in the MRU list (which we might be able to tweak via mtimes). But
> > hopefully in the "after" state it should deterministically complain
> > about $X.
> 
> Yeah. The problem I had here is that I'm not sure whether we have any
> tools to reliably create a corrupted object, e.g. with a hash mismatch.
> I'll have a look for v2.

You can see how do_corrupt_object() in t5303 does it. It's basically finding an offset via show-index and then writing a zero over it with dd.

-Peff
Previous: Patrick SteinhardtNext: Patrick Steinhardt
Message 18 of 26 in “pack-check: fix verification of large objects”
  1. 0/4 pack-check: fix verification of large objectsPatrick Steinhardt, Feb 23, 2026
  2. 1/4 t/helper: improve "genrandom" test helperPatrick Steinhardt, Feb 23, 2026
  3. Jeff KingFeb 23, 2026
  4. Patrick SteinhardtFeb 23, 2026
  5. Eric SunshineFeb 23, 2026
  6. 2/4 object-file: adapt `stream_object_signature()` to take a streamPatrick Steinhardt, Feb 23, 2026
  7. Jeff KingFeb 23, 2026
  8. Patrick SteinhardtFeb 23, 2026
  9. Jeff KingFeb 23, 2026
  10. 3/4 packfile: expose function to read object stream for an offsetPatrick Steinhardt, Feb 23, 2026
  11. Jeff KingFeb 23, 2026
  12. Patrick SteinhardtFeb 23, 2026
  13. Jeff KingFeb 23, 2026
  14. Patrick SteinhardtFeb 23, 2026
  15. 4/4 pack-check: fix verification of large objectsPatrick Steinhardt, Feb 23, 2026
  16. Jeff KingFeb 23, 2026
  17. Patrick SteinhardtFeb 23, 2026
  18. Jeff KingFeb 23, 2026
  19. Patrick SteinhardtFeb 23, 2026
  20. Junio C HamanoFeb 23, 2026
  21. Patrick SteinhardtFeb 24, 2026
  22. 0/4 pack-check: fix verification of large objectsPatrick Steinhardt, Feb 23, 2026
  23. 1/4 t/helper: improve "genrandom" test helperPatrick Steinhardt, Feb 23, 2026
  24. 2/4 object-file: adapt `stream_object_signature()` to take a streamPatrick Steinhardt, Feb 23, 2026
  25. 3/4 packfile: expose function to read object stream for an offsetPatrick Steinhardt, Feb 23, 2026
  26. 4/4 pack-check: fix verification of large objectsPatrick Steinhardt, Feb 23, 2026

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