- wal.c: wo_wal_fold_row_at now refuses any delta back-pointer that
does not point strictly earlier than the record naming it
(back_off >= cur), instead of capping total hops at off/13+1
- this is the real invariant, not a proxy for it: a step-count bound
lets a forward-pointing back-pointer through in one hop whenever it
happens to land on a genuine record, returning a plausible-but-wrong
row instead of refusing it
- removes the 13-byte-record magic number entirely; no arithmetic
tied to record framing remains in the guard
- wal.h: docblock updated to describe the direction invariant
- test_wal.c: two new tests — self-pointing back-pointer (boundary
case, back_off == cur) and forward-pointing back-pointer to a real
future record for the same row (the actual gap: verified failing
against the old step-count guard, passing after the fix)
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
(cherry picked from commit 173dbf28a42d45a8c7f9fe430355f61f70c81935)
shoney.arickathil
b758f2978d