From 2f21ec39adcfc3a2ce4d4fd08eb1fa688c4e67a7 Mon Sep 17 00:00:00 2001
From: Marco Costalba <mcostalba@gmail.com>
Date: Sun, 22 Feb 2009 18:03:23 +0100
Subject: [PATCH] Convert also undo_null_move() to avoid passing UndoInfo
 object

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
---
 src/position.cpp | 18 +++++++++++-------
 src/position.h   |  2 +-
 src/search.cpp   |  2 +-
 3 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/src/position.cpp b/src/position.cpp
index 21b00f80..c6c31527 100644
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -1445,10 +1445,12 @@ void Position::do_null_move(UndoInfo& u) {
   assert(!is_check());
 
   // Back up the information necessary to undo the null move to the supplied
-  // UndoInfo object.  In the case of a null move, the only thing we need to
+  // UndoInfo object. In the case of a null move, the only thing we need to
   // remember is the last move made and the en passant square.
   u.lastMove = lastMove;
   u.epSquare = epSquare;
+  u.previous = previous;
+  previous = &u;
 
   // Save the current key to the history[] array, in order to be able to
   // detect repetition draws.
@@ -1473,18 +1475,20 @@ void Position::do_null_move(UndoInfo& u) {
 
 /// Position::undo_null_move() unmakes a "null move".
 
-void Position::undo_null_move(const UndoInfo &u) {
+void Position::undo_null_move() {
 
   assert(is_ok());
   assert(!is_check());
 
-  // Restore information from the supplied UndoInfo object:
-  lastMove = u.lastMove;
-  epSquare = u.epSquare;
+  // Restore information from the our UndoInfo object
+  lastMove = previous->lastMove;
+  epSquare = previous->epSquare;
+  previous = previous->previous;
+
   if (epSquare != SQ_NONE)
       key ^= zobEp[epSquare];
 
-  // Update the necessary information.
+  // Update the necessary information
   sideToMove = opposite_color(sideToMove);
   rule50--;
   gamePly--;
@@ -1942,7 +1946,7 @@ bool Position::has_mate_threat(Color c) {
 
   // Undo null move, if necessary
   if (c != stm)
-      undo_null_move(u1);
+      undo_null_move();
 
   return result;
 }
diff --git a/src/position.h b/src/position.h
index c132c8f8..7300c9d7 100644
--- a/src/position.h
+++ b/src/position.h
@@ -244,7 +244,7 @@ public:
   void do_move(Move m, UndoInfo &u);
   void undo_move(Move m);
   void do_null_move(UndoInfo &u);
-  void undo_null_move(const UndoInfo &u);
+  void undo_null_move();
 
   // Static exchange evaluation
   int see(Square from, Square to) const;
diff --git a/src/search.cpp b/src/search.cpp
index 3b81fa86..8c847714 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1201,7 +1201,7 @@ namespace {
             && pos.see(ss[ply + 1].currentMove) + nullValue >= beta)
             nullDrivenIID = true;
 
-        pos.undo_null_move(u);
+        pos.undo_null_move();
 
         if (value_is_mate(nullValue))
         {
-- 
2.39.2