(svn r19433) -Codechange: Limit rail clearance earnings to 3/4s of rail build cost, to avoid money making loophole when rail build cost is less than rail removal earnings.

2 files changed, 22 insertions, 2 deletions

diff --git a/src/rail.h b/src/rail.h
index 3f401cd37..f0a5ef609 100644
--- a/src/rail.h
+++ b/src/rail.h
@@ -270,6 +270,22 @@ static inline Money RailBuildCost(RailType railtype)
 }
 
 /**
+ * Returns the 'cost' of clearing the specified railtype.
+ * @param railtype The railtype being removed.
+ * @return The cost.
+ */
+static inline Money RailClearCost(RailType railtype)
+{
+	/* Clearing rail in fact earns money, but if the build cost is set
+	 * very low then a loophole exists where money can be made.
+	 * In this case we limit the removal earnings to 3/4s of the build
+	 * cost.
+	 */
+	assert(railtype < RAILTYPE_END);
+	return max(_price[PR_CLEAR_RAIL], -RailBuildCost(railtype) * 3 / 4);
+}
+
+/**
  * Calculates the cost of rail conversion
  * @param from The railtype we are converting from
  * @param to   The railtype we are converting to
@@ -296,7 +312,7 @@ static inline Money RailConvertCost(RailType from, RailType to)
 	}
 
 	/* make the price the same as remove + build new type */
-	return RailBuildCost(to) + _price[PR_CLEAR_RAIL];
+	return RailBuildCost(to) + RailClearCost(from);
 }
 
 void DrawTrainDepotSprite(int x, int y, int image, RailType railtype);
diff --git a/src/rail_cmd.cpp b/src/rail_cmd.cpp
index f0b79a070..7440f86ac 100644
--- a/src/rail_cmd.cpp
+++ b/src/rail_cmd.cpp
@@ -503,7 +503,7 @@ CommandCost CmdBuildSingleRail(TileIndex tile, DoCommandFlag flags, uint32 p1, u
 CommandCost CmdRemoveSingleRail(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Track track = (Track)p2;
-	CommandCost cost(EXPENSES_CONSTRUCTION, _price[PR_CLEAR_RAIL] );
+	CommandCost cost(EXPENSES_CONSTRUCTION);
 	bool crossing = false;
 
 	if (!ValParamTrackOrientation((Track)p2)) return CMD_ERROR;
@@ -533,6 +533,8 @@ CommandCost CmdRemoveSingleRail(TileIndex tile, DoCommandFlag flags, uint32 p1,
 				if (ret.Failed()) return ret;
 			}
 
+			cost.AddCost(RailClearCost(GetRailType(tile)));
+
 			if (flags & DC_EXEC) {
 				if (HasReservedTracks(tile, trackbit)) {
 					v = GetTrainForReservation(tile, track);
@@ -563,6 +565,8 @@ CommandCost CmdRemoveSingleRail(TileIndex tile, DoCommandFlag flags, uint32 p1,
 			if ((present & trackbit) == 0) return CMD_ERROR;
 			if (present == (TRACK_BIT_X | TRACK_BIT_Y)) crossing = true;
 
+			cost.AddCost(RailClearCost(GetRailType(tile)));
+
 			/* Charge extra to remove signals on the track, if they are there */
 			if (HasSignalOnTrack(tile, track))
 				cost.AddCost(DoCommand(tile, track, 0, flags, CMD_REMOVE_SIGNALS));