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Fix crash under Chess 960

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We have a crash with this position:

rkqbnnbr/pppppppp/8/8/8/8/PPPPPPPP/RKQBNNBR w HAha -

What happens is that even if we are castling QUEEN_SIDE,
in this case we have kfrom (B8) < kto (C8) so the loop
that checks for attackers runs forever leading to a crash.

The fix is to check for (kto > kfrom) instead of
Side == KING_SIDE, but this is slower in the normal case of
ortodhox chess, so rewrite generate_castle() to handle the
chess960 case as a template parameter and allow the compiler
to optimize out the comparison in case of normal chess.

Reported by Ray Banks.
This commit is contained in:
Marco Costalba 2012-09-16 14:06:13 +02:00
parent 9ce7469846
commit 22a5f91aa7
1 changed files with 17 additions and 7 deletions
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24
src/movegen.cpp
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@ -31,7 +31,7 @@
(*mlist++).move = make_move(to - (d), to); }
namespace {
template<CastlingSide Side, bool Checks>
template<CastlingSide Side, bool Checks, bool Chess960>
MoveStack* generate_castle(const Position& pos, MoveStack* mlist, Color us) {
if (pos.castle_impeded(us, Side) || !pos.can_castle(make_castle_right(us, Side)))
@ -46,16 +46,18 @@ namespace {
assert(!pos.in_check());
for (Square s = kto; s != kfrom; s += (Square)(Side == KING_SIDE ? -1 : 1))
const int K = Chess960 ? kto > kfrom ? -1 : 1
: Side == KING_SIDE ? -1 : 1;
for (Square s = kto; s != kfrom; s += (Square)K)
if (pos.attackers_to(s) & enemies)
return mlist;
// Because we generate only legal castling moves we need to verify that
// when moving the castling rook we do not discover some hidden checker.
// For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
if ( pos.is_chess960()
&& (pos.attackers_to(kto, pos.pieces() ^ rfrom) & enemies))
return mlist;
if (Chess960 && (pos.attackers_to(kto, pos.pieces() ^ rfrom) & enemies))
return mlist;
(*mlist++).move = make<CASTLE>(kfrom, rfrom);
@ -273,8 +275,16 @@ namespace {
if (Type != CAPTURES && Type != EVASIONS && pos.can_castle(us))
{
mlist = generate_castle<KING_SIDE, Type == QUIET_CHECKS>(pos, mlist, us);
mlist = generate_castle<QUEEN_SIDE, Type == QUIET_CHECKS>(pos, mlist, us);
if (pos.is_chess960())
{
mlist = generate_castle<KING_SIDE, Type == QUIET_CHECKS, true>(pos, mlist, us);
mlist = generate_castle<QUEEN_SIDE, Type == QUIET_CHECKS, true>(pos, mlist, us);
}
else
{
mlist = generate_castle<KING_SIDE, Type == QUIET_CHECKS, false>(pos, mlist, us);
mlist = generate_castle<QUEEN_SIDE, Type == QUIET_CHECKS, false>(pos, mlist, us);
}
}
return mlist;