From: Fabian Fichter <ianfab@users.noreply.github.com>
Date: Mon, 30 Dec 2024 12:54:58 +0000 (+0100)
Subject: Handle invalid castling FEN
X-Git-Url: http://winboard.nl/cgi-bin?a=commitdiff_plain;h=4d8f3d27d156c47d6a3bd35a3a1bfe082fa270eb;p=fairystockfish.git

Handle invalid castling FEN

Closes #826.
---

diff --git a/src/position.cpp b/src/position.cpp
index bd4adc8..40fa6e3 100644
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -362,10 +362,10 @@ Position& Position::set(const Variant* v, const string& fenStr, bool isChess960,
           token = char(toupper(token));
 
           if (castling_enabled() && token == 'K')
-              for (rsq = make_square(var->castlingRookKingsideFile, castling_rank(c)); !(castling_rook_pieces(c) & type_of(piece_on(rsq))) || color_of(piece_on(rsq)) != c; --rsq) {}
+              for (rsq = make_square(var->castlingRookKingsideFile, castling_rank(c)); (!(castling_rook_pieces(c) & type_of(piece_on(rsq))) || color_of(piece_on(rsq)) != c) && file_of(rsq) > FILE_A; --rsq) {}
 
           else if (castling_enabled() && token == 'Q')
-              for (rsq = make_square(var->castlingRookQueensideFile, castling_rank(c)); !(castling_rook_pieces(c) & type_of(piece_on(rsq))) || color_of(piece_on(rsq)) != c; ++rsq) {}
+              for (rsq = make_square(var->castlingRookQueensideFile, castling_rank(c)); (!(castling_rook_pieces(c) & type_of(piece_on(rsq))) || color_of(piece_on(rsq)) != c) && file_of(rsq) < max_file(); ++rsq) {}
 
           else if (token >= 'A' && token <= 'A' + max_file())
               rsq = make_square(File(token - 'A'), castling_rank(c));
@@ -382,6 +382,12 @@ Position& Position::set(const Variant* v, const string& fenStr, bool isChess960,
               st->castlingKingSquare[c] =  isChess960 && piece_on(rsq) == make_piece(c, castling_king_piece(c)) ? rsq
                                          : castlingKings && (!more_than_one(castlingKings) || isChess960) ? lsb(castlingKings)
                                          : make_square(castling_king_file(), castling_rank(c));
+              // Skip invalid castling rights
+              if (!(castlingKings & st->castlingKingSquare[c]))
+              {
+                  st->castlingKingSquare[c] = SQ_NONE;
+                  continue;
+              }
           }
 
           // Set gates (and skip castling rights)
diff --git a/test.py b/test.py
index 0999589..9198914 100644
--- a/test.py
+++ b/test.py
@@ -427,6 +427,12 @@ class TestPyffish(unittest.TestCase):
         result = sf.get_fen("chess", "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w 1 2", [])
         self.assertEqual(result, "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w - - 1 2")
 
+        # invalid castling rights
+        result = sf.get_fen("chess", "8/rnbqkbnr/pppppppp/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1", [])
+        self.assertEqual(result, "8/rnbqkbnr/pppppppp/8/8/8/PPPPPPPP/RNBQKBNR w KQ - 0 1")
+        result = sf.get_fen("chess", "r7/1nbqkbnr/pppppppp/8/8/P6P/RPPPPPPR/1NBQKBN1 w KQkq - 0 1", [])
+        self.assertEqual(result, "r7/1nbqkbnr/pppppppp/8/8/P6P/RPPPPPPR/1NBQKBN1 w - - 0 1")
+
         # alternative piece symbols
         result = sf.get_fen("janggi", "rhea1aehr/4k4/1c5c1/p1p1p1p1p/9/9/P1P1P1P1P/1C5C1/4K4/RHEA1AEHR w - - 0 1", [])
         self.assertEqual(result, JANGGI)