Scoring crash

[gunnar]

 http://lists.gnu.org/archive/html/gnugo-devel/2005-04/msg00010.html

I haven't yet had time to investigate this, but I found the following
crash (run final_score in gtp mode on the sgf).  It is reproducible in
current CVS.

Evan


***assertion failure:
board.c:2645 - board[pos] == EMPTY near E3***

 (variation 59741)
   A B C D E F G H J
 9 . . . X X O . O . 9
 8 . . X X O O O O O 8
 7 . X O X X X O . . 7
 6 . . . X X O O O O 6
 5 . . . X + X X O X 5
 4 . . X . O X . X X 4
 3 . . X . X O X X X 3
 2 . . X X O O . . . 2     WHITE (O) has captured 0 stones
 1 . . . . X O . . . 1     BLACK (X) has captured 6 stones
   A B C D E F G H J
(;GM[1]FF[4]SZ[9]KM[0.0]GN[GNU Go 3.7.2 stepped on a bug]
;B[cg];W[gd];B[dd];W[fg];B[fc];W[gc];B[ed];W[cc];B[db];W[dg];B[cf];W[fb]
;B[cb];W[fd];B[dh];W[eh];B[ch];W[df];B[de];W[ef];B[fe];W[ee];B[ec];W[eb]
;B[ea];W[gb];B[ei];W[fi];B[ff];W[gf];B[eg];W[fh];B[ge];W[he];B[hf];W[if]
;B[hg];W[ef];B[gg];W[id];B[ig];W[fa];B[da];W[ib];B[ie];W[hd];B[if];W[]
;B[];W[];B[];W[ha];B[bc];W[hb];B[dc]
)
gnugo 3.7.2 (seed 0): You stepped on a bug.

[gunnar]

There are three issues conspiring to cause this crash.

1. The D9 dragon is evaluated to status UNKNOWN.
2. Line 673 of aftermath.c tests status != ALIVE, thereby counting D9 as something that should be taken off the board,
3. The test at line 757 that a backfilling move to avoid self-atari really isn't a self-atari should first check that the point isn't occupied.

[gunnar]

bugfixes in aftermath.c

[gunnar]

For issue 1, see ticket #35.

Issues 2 and 3 are fixed by the attached patch gunnar_7_8.4.

- bugfixes in do_aftermath_genmove()