fix(math): stop cbrt from misclassifying negative normals as subnormal - #3938
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Kaida-Amethyst merged 2 commits intoAug 4, 2026
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Closes moonbitlang#3909 Signed-off-by: 林晨 (Leo Cheng) <leo-cheng@vip.qq.com>
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August 4, 2026 07:14
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cbrtread the high word as a signed int and used it directly for the subnormal testhx < 0x00100000. For a negative normal input the sign bit makeshxnegative, so it always compares as less than the threshold and takes the subnormal branch, giving an inaccurate result (about 7741 ULP off for-2^971). The sign is already tracked separately, so masking it off (& 0x7fffffff, as the original musl code does) is enough.Added a regression test for a large negative normal plus an odd-symmetry check.
Closes #3909