From: H.G. Muller <h.g.muller@hccnet.nl>
Date: Wed, 28 Mar 2012 21:51:28 +0000 (+0200)
Subject: Fix bug in FRC castling for position search
X-Git-Url: http://winboard.nl/cgi-bin?a=commitdiff_plain;h=e3af409047e1992a08e296c1475c94b8a1e5f7b1;p=xboard.git

Fix bug in FRC castling for position search

In FRC it is essential that both pieces are taken off the board before
any of them is put back, lest they obliterate each other.
---

diff --git a/backend.c b/backend.c
index e474fd4..38c3533 100644
--- a/backend.c
+++ b/backend.c
@@ -11515,7 +11515,7 @@ QuickCompare (Board board, int *minCounts, int *maxCounts)
 int
 QuickScan (Board board, Move *move)
 {   // reconstruct game,and compare all positions in it
-    int cnt=0, stretch=0, total = MakePieceList(board, counts);
+    int cnt=0, stretch=0, total = MakePieceList(board, counts), delayedKing = -1;
     do {
 	int piece = move->piece;
 	int to = move->to, from = pieceList[piece];
@@ -11533,18 +11533,22 @@ QuickScan (Board board, Move *move)
 	    move++;
 	    continue;
 	  } else if(piece <= Q_BCASTL) { // castling, encoded as (Q_XCASTL, king-to) + (rook, rook-to)
+	    int rook;
 	    piece = pieceList[piece]; // first two elements of pieceList contain King numbers
 	    from  = pieceList[piece]; // so this must be King
 	    quickBoard[from] = 0;
-	    quickBoard[to] = piece;
 	    pieceList[piece] = to;
-	    move++;
-	    continue;
+	    from = pieceList[(++move)->piece]; // for FRC this has to be done here
+	    quickBoard[from] = 0; // rook
+	    quickBoard[to] = piece;
+	    to = move->to; piece = move->piece;
+	    goto aftercastle;
 	  }
 	}
 	if(appData.searchMode > 2) counts[pieceType[quickBoard[to]]]--; // account capture
 	if((total -= (quickBoard[to] != 0)) < soughtTotal) return -1; // piece count dropped below what we search for
 	quickBoard[from] = 0;
+      aftercastle:
 	quickBoard[to] = piece;
 	pieceList[piece] = to;
 	cnt++; turn ^= 3;
@@ -11559,7 +11563,7 @@ QuickScan (Board board, Move *move)
 	    if(stretch++ == 0) for(i=0; i<EmptySquare; i++) lastCounts[i] = counts[i]; // remember actual material
 	} else stretch = 0;
 	if(stretch && (appData.searchMode == 1 || stretch >= appData.stretch)) return cnt + 1 - stretch;
-	move++;
+	move++; delayedKing = -1;
     } while(1);
 }