-extern Bitboard SquaresByColorBB[2];
-extern Bitboard FileBB[8];
-extern Bitboard NeighboringFilesBB[8];
-extern Bitboard ThisAndNeighboringFilesBB[8];
-extern Bitboard RankBB[8];
-extern Bitboard InFrontBB[2][8];
+extern const Bitboard SquaresByColorBB[2];
+extern const Bitboard FileBB[8];
+extern const Bitboard NeighboringFilesBB[8];
+extern const Bitboard ThisAndNeighboringFilesBB[8];
+extern const Bitboard RankBB[8];
+extern const Bitboard InFrontBB[2][8];