Crash in variant Coffeehouse

[autocorr]

There appears to be a segfault in the variant "coffeehouse" when null moves are generated. It happens frequently on the fishnet worker I use, but is also reproducible from (most) of the same positions on fairyground. The variant definition used can be found below:

[coffeehouse:crazyhouse]
mustCapture = true

An example can be reproduced on fairyground by setting multipv to 2, hash to 256 MB, threads to 4, and an initial move for White of f2f3 then starting analysis. After reaching a search depth of around 9, a null/invalid move is reached in the second line and the engine subsequently crashes. Interestingly this particular move doesn't force a capture.

I don't have much more insight into the cause, except that raising the hash size tends make the errors less frequent. Reading through the current issues, it's possible that this is also related to #800 , since this definition inherits from ZH. Although I can't do it today, I can test a definition without inheritance soon to see if that works around the problem.

Edit: I tried inheriting directly from chess by adding the rules for Crazyhouse to the definition (see below), and it seems to have worked around the issue.

[coffeehouse:chess]
startFen = rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR[] w KQkq - 0 1
pieceDrops = true
capturesToHand = true
mustCapture = true

[ianfab]

Thanks. Can you reproduce this with native Fairy-SF? So far I failed to reproduce it regardless of multipv, hash, and thread setting, even with debug=yes.