Re: [gnugo-devel] board.c:3319 - color == WHITE || color == BLACK near F16

[Gunnar Farneback]

Dan wrote:
> IL is a private SGF property used by GNU Go to mark the location
> of an illegal move, usually a ko capture.
> 
> So it is no surprise that stripping this property will break
> a regression. However it is not clear why it would cause a crash.

It's not stripped. The SGF spec requires that unknown properties are
retained and sgfc naturally complies with this.

The reason for the crash is that that the conversion of AB properties
into ranges causes GNU Go to only see the first stone in each range.
When it then tries to determine whether an illegal point is due to ko
rather than suicide it assumes that all surrounding vertices are
either off the board or occupied by stones. When this is not true an
assertion fails.

/Gunnar