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Make wide-dedup XXH3 parity tests safe under ARM64 sanitizers

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
67/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
c
Domain
embedded-iot, testing

Research direction

Start with test_wide_dedup_hash_without_allocation and the ARM64 sanitizer failure described in the linked CI run; compare its expected-hash input with the production wide-row path. Keep the parity checks for widths 9 and 32 and the no-allocation assertion, then run test_tdd_recursive under ARM64 ASan/UBSan. Done when it passes without alignment diagnostics or weakened checks.

Written by the indexing model from the issue text.

Description

p2-medium track/platform

Discovery context

The ARM64 sanitizer job for PR #1903 (issue #1369) aborted in CI run 35935910267, job 107433007078, while running tdd_recursive. UBSan reported a misaligned load of xxh_aliasing_uint64x2_t in the pinned xxHash 0.8.4 xxhash.h:4150. The wide-dedup parity test passes a stack int64_t[32] directly to contiguous XXH3_64bits; the production wide-row path instead streams scalar values.

Architect and Critic reviewed this as test-oracle alignment portability, separate from #1369's memory-admission behavior. Preserve the sanitizer evidence and parity/no-allocation assertions when fixing it.

Scope

Make the expected-hash input in test_wide_dedup_hash_without_allocation explicitly aligned for the ARM64 xxHash vector path, or use an equivalent sanitizer-safe reference calculation. Keep the change in test code; do not change production dedup behavior, vendor or upgrade xxHash, suppress UBSan, or weaken alignment checks.

Acceptance criteria

  • test_tdd_recursive passes under ARM64 ASan/UBSan with no alignment diagnostics.
  • The wide-row parity checks still cover widths 9 and 32, and the no-allocation assertion remains.
  • The relevant ARM64 sanitizer target passes without test exclusions, sanitizer suppressions, or weakened compiler/runtime checks.
  • The pinned dependency and reproducible test setup remain documented.
Dominant language
C
Stars
18
Forks
2
Avg merge
11h 33m
Merged PRs (30d)
296

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