Show move that causes false illegal-move claim

Without claim testing XBoard takes back moves that an engine objects to.
But when the engine is forfeited for a false claim, the move should of
course stay. So the claim test is moved to before the take-back.

diff --git a/backend.c b/backend.c
index b48ea5f..8169707 100644 (file)
--- a/backend.c
+++ b/backend.c
@@ -7691,6 +7691,13 @@ if(appData.debugMode) fprintf(debugFP, "nodes = %d, %lld\n", (int) programStats.
            gameMode = EditGame;
            ModeHighlight();
        }
+        /* [HGM] illegal-move claim should forfeit game when Xboard */
+        /* only passes fully legal moves                            */
+        if( appData.testLegality && gameMode == TwoMachinesPlay ) {
+            GameEnds( cps->twoMachinesColor[0] == 'w' ? BlackWins : WhiteWins,
+                                "False illegal-move claim", GE_XBOARD );
+            return; // do not take back move we tested as valid
+        }
        currentMove = forwardMostMove-1;
        DisplayMove(currentMove-1); /* before DisplayMoveError */
        SwitchClocks(forwardMostMove-1); // [HGM] race
@@ -7699,13 +7706,6 @@ if(appData.debugMode) fprintf(debugFP, "nodes = %d, %lld\n", (int) programStats.
                parseList[currentMove], cps->which);
        DisplayMoveError(buf1);
        DrawPosition(FALSE, boards[currentMove]);
-
-        /* [HGM] illegal-move claim should forfeit game when Xboard */
-        /* only passes fully legal moves                            */
-        if( appData.testLegality && gameMode == TwoMachinesPlay ) {
-            GameEnds( cps->twoMachinesColor[0] == 'w' ? BlackWins : WhiteWins,
-                                "False illegal-move claim", GE_XBOARD );
-        }
        return;
     }
     if (strncmp(message, "time", 4) == 0 && StrStr(message, "Illegal")) {