From: Marco Costalba <mcostalba@gmail.com>
Date: Mon, 23 Feb 2009 17:46:33 +0000 (+0100)
Subject: Fix a subtle bug due to the StateInfo pointer became stale
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=55f9afee2a079b2dd0b1aeda41082c58eb317ca3

Fix a subtle bug due to the StateInfo pointer became stale

There was one occurence when the StateInfo variable went
out of scope before the corresponding Position object.

This yelds to a crash. Bug was not hit before because occurs
only when using an UCI interface and not the usual benchmark.

The fix consists in copying internally the content of the
about to stale StateInfo.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
---

diff --git a/src/position.cpp b/src/position.cpp
index 0a275b5e..7725b934 100644
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -1662,6 +1662,18 @@ int Position::see(Square from, Square to) const {
 }
 
 
+/// Position::setStartState() copies the content of the argument
+/// inside startState and makes st point to it. This is needed
+/// when the st pointee could become stale, as example because
+/// the caller is about to going out of scope.
+
+void Position::setStartState(const StateInfo& s) {
+
+  startState = s;
+  st = &startState;
+}
+
+
 /// Position::clear() erases the position object to a pristine state, with an
 /// empty board, white to move, and no castling rights.
 
diff --git a/src/position.h b/src/position.h
index ae750697..676f68ef 100644
--- a/src/position.h
+++ b/src/position.h
@@ -240,6 +240,7 @@ public:
   bool square_is_weak(Square s, Color c) const;
 
   // Doing and undoing moves
+  void setStartState(const StateInfo& st);
   void do_move(Move m, StateInfo& st);
   void undo_move(Move m);
   void do_null_move(StateInfo& st);
diff --git a/src/uci.cpp b/src/uci.cpp
index b03752ed..6ce3bf85 100644
--- a/src/uci.cpp
+++ b/src/uci.cpp
@@ -22,6 +22,7 @@
 //// Includes
 ////
 
+#include <cassert>
 #include <iostream>
 #include <sstream>
 #include <string>
@@ -228,6 +229,9 @@ namespace {
                 if (RootPosition.rule_50_counter() == 0)
                     RootPosition.reset_game_ply();
             }
+            // Our StateInfo st is about going out of scope,
+            // so save its content before they disappear.
+            RootPosition.setStartState(st);
         }
     }
   }
@@ -321,6 +325,8 @@ namespace {
     if (moveTime)
         infinite = true;  // HACK
 
+    assert(RootPosition.is_ok());
+
     think(RootPosition, infinite, ponder, RootPosition.side_to_move(), time,
           inc, movesToGo, depth, nodes, moveTime, searchMoves);
   }