Application crashes on checkmate about chessmarkable HOT 4 CLOSED

I have just seen that the issue #1 is related to this. The position in the picture is a checkmate for white.

No, there was no checkmate message.

In the case of checkmate (and of stalemate), the player has no legal move. I don't know what the engine attempts to do in this case, but from your comment in issue #1, it sounds like the engine attempts an illegal move instead. If this is the case, I would suggest you handle it this way:

• Don't play the illegal move, because it is just the engine assuming that the game is over
• If the engine is in a check position (and has no legal moves), it is a checkmate
• If the engine is not in a check position (and has no legal moves), it is a stalemate (draw)

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I had some struggle with that already. The things is that the bot tends to make non-moving moves (just moves from src to dest) when the king is cornered. As far as I understand it, this is not legal at all. Some check (gives_check(...) or similar) does a assert against that which is why I replaced it with a null move. But this is also a quite hacky solution. I need to look up better ways on that.

Did the "Checkmate!" appear before the crash?

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Good idea. I could reproduce the bug on checkmating the bot as well. I'll try to fix that in the evening (in about 6 hours) since I have lectures atm. I'll also probably add the possibility to import/export the board as FEN to speed up testing your suggested fix which sounds promising.

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I think that I have sorted it out now. It now recognized a stalemate and check even before the bot tries to pull as "null move".

Here is a FEN that can easily result in a stalemate: 8/8/2Q5/4k3/1R6/8/6K1/8 w - - 0 46 (start with this state by setting -i to it).
This one can be used to checkmate the black: 1R7/8/2Q5/4k3/1R6/8/6K1/8 w - - 0 46 (just added another rook to the mix).

Seems to work fine now. Let me know if you still manage to crash it.

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