I don't know whether it applies here, but if I understand correctly,
I've added some more tests to see if I could make it fail. Microsoft's UpdateSemantics is not very picky. I can't get it to return anything but D3D_OK except for when I pass a null pointer. My implementation follows this behavior except for two cases: it returns E_FAIL when passing an undefined type and when the offset is not 4 byte aligned. This is because the values are checked inside vertexdeclaration_init. So Wine is stricter. I don't think that it is necessarily a problem because applications that pass bogus declarations like those will likely not work anyway. My own tests with a small interactive demo show that in those cases the application will crash with an access violation when it tries to re-draw the scene.