Fix flaky TestSetAndGetUUIDValue: big.Int drops leading zero bytes#518
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lemire merged 1 commit intoRoaringBitmap:masterfrom Mar 9, 2026
Merged
Fix flaky TestSetAndGetUUIDValue: big.Int drops leading zero bytes#518lemire merged 1 commit intoRoaringBitmap:masterfrom
lemire merged 1 commit intoRoaringBitmap:masterfrom
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…eros big.Int.Bytes() returns the minimal-length byte slice with no leading zeros. When the UUID binary representation happens to start with 0x00 (probability ~1/256), the round-trip through big.Int loses that byte, producing 15 bytes instead of 16. uuid.FromBytes then rejects the result. Fix by using big.Int.FillBytes, which left-pads with zeros to exactly fill the destination slice. Also add a deterministic regression test, TestSetAndGetUUIDValueLeadingZero, which constructs a UUID with a known leading zero byte so the failure mode can be reproduced without relying on randomness.
lemire
reviewed
Mar 9, 2026
| assert.Equal(t, bigUUID, bv) | ||
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| newUUID, err := uuid.FromBytes(bv.Bytes()) | ||
| // big.Int.Bytes() drops leading zero bytes; use FillBytes to restore the |
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Summary
TestSetAndGetUUIDValuefails intermittently (~1/256 runs) when the UUIDbinary representation starts with a
0x00byte.big.Int.Bytes()returnsthe minimal-length byte slice with no leading zeros, so that byte is
silently dropped, producing 15 bytes instead of 16.
uuid.FromBytesthenrejects the result with "invalid UUID (got 15 bytes)".
Fix: use
big.Int.FillBytesinstead, which left-pads with zeros toexactly fill the destination slice.
Also adds
TestSetAndGetUUIDValueLeadingZero, a deterministic regressiontest that constructs a UUID with a known leading zero byte so the failure
mode is reproducible without relying on randomness.
Verified by running
TestSetAndGetUUIDValuewith-count=500before andafter the fix: the unfixed test reliably produces a failure within that
window; the fixed test passes all 500 runs.
This was flagged by the macOS CI failure on #515, which is otherwise an
unrelated change. The Linux runners happened to not hit the 1/256 case in
that run.