[matt-edmondson]

Fixes #464

What was wrong

StorageMath.RootN handled a negative value with an odd degree by returning -RootN(-value, n). For a two's-complement integer's MinValue, -value wraps back to MinValue. RootN therefore called itself with the same arguments until the stack overflowed, which ends the process. This hit Cbrt(sbyte.MinValue), RootN(int.MinValue, 5), and the MinValue of short, long and Int128.

Change

• When negating gives a value that is still negative, RootN roots -(value + 1), the magnitude one below. The floors of the two roots differ only when |MinValue| is itself an exact nth power, and then by exactly one.
• A new IsExactPower helper checks that case by dividing value by the candidate root n times, to see whether it leaves exactly -1. Division keeps everything in range, so nothing overflows.
• The result keeps the documented contract: the floor towards zero, and the exact root where there is one. For example, Cbrt(long.MinValue) is -2097152 (2^21) and RootN(sbyte.MinValue, 7) is -2.
• Ordinary negative inputs take the same path as before. The even-root branch is unchanged, only reshaped into an if.

Tests

New test: OddRootOfIntegerMinValueIsTheExactFloor. It covers sbyte, short, int, long and Int128 with Cbrt and odd RootN, including the exact-power cases. The expected values were cross-checked with arbitrary-precision integer arithmetic.

• With the StorageMath.cs change reverted, the test host dies with Stack overflow.
• With the change, the full suite passes: 1780 succeeded, 0 failed locally on net10.0. The net9.0 leg could not launch in my environment, which has no .NET 9 runtime.

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Generated by Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

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