Impossible position

[smrf]

There is an erroneous assumption. It is: while own king is not in check a move could only be illegal when being pinned. But this does not hold as you can see analyzing the example above. Thus especially after an e.p. capture the validity test has to be extended.

P.S.: Also see following example:

[d]

[cms271828]

Some good advice there, the position with the bishop in front of the row of pawns made me laugh.

My thoughts are to test this situation regarding the en passant in my board setup options, and then assume it will not occur during a game, which it shouldn't.

I'm guessing this is the only situation that can crash an engine, but could be something else I overlooked.