[C#] Fix union verifier #8593
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[C#] Fix union verifier #8593
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bjornharrtell
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PR and motivation for this seems sensible but I know too little about the verifier to be entirely sure about it's correctness. @aardappel does it seem right to do this fix?
aardappel
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Aug 28, 2025
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aardappel
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Yup this makes sense to me, thanks!
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There seems to be a bug in
Verifyer::VerifyUnion: The offset of the union type is extracted and checked, but overwritten by the offset of the value before reading out the typeId of the union, leading to the typeId being incorrect.In the typical case, the offset of the value is larger than the largest typeId in the union, leaving the verifier to assume that the union is from a future schema version. This means that the union value is never verified.
The first commit in this PR adds a unit test that fails due to this bug.
The second commit fixes the bug.