(svn r19405) -Codechange: CheckOwnership() returns a CommandCost.

src/aircraft_cmd.cpp

@@ -405,13 +405,17 @@ CommandCost CmdBuildAircraft(TileIndex tile, DoCommandFlag flags, uint32 p1, uin
 CommandCost CmdSellAircraft(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Aircraft *v = Aircraft::GetIfValid(p1);
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
 	if (!v->IsStoppedInDepot()) return_cmd_error(STR_ERROR_AIRCRAFT_MUST_BE_STOPPED);
 
 	if (v->vehstatus & VS_CRASHED) return_cmd_error(STR_ERROR_CAN_T_SELL_DESTROYED_VEHICLE);
 
-	CommandCost ret(EXPENSES_NEW_VEHICLES, -v->value);
+	ret = CommandCost(EXPENSES_NEW_VEHICLES, -v->value);
 
 	if (flags & DC_EXEC) {
 		delete v;
@@ -480,7 +484,12 @@ CommandCost CmdRefitAircraft(TileIndex tile, DoCommandFlag flags, uint32 p1, uin
 	byte new_subtype = GB(p2, 8, 8);
 
 	Aircraft *v = Aircraft::GetIfValid(p1);
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
+
 	if (!v->IsStoppedInDepot()) return_cmd_error(STR_ERROR_AIRCRAFT_MUST_BE_STOPPED);
 	if (v->vehstatus & VS_CRASHED) return_cmd_error(STR_ERROR_CAN_T_REFIT_DESTROYED_VEHICLE);
 

src/autoreplace_cmd.cpp

@@ -628,7 +628,10 @@ CommandCost CmdAutoreplaceVehicle(TileIndex tile, DoCommandFlag flags, uint32 p1
 	Vehicle *v = Vehicle::GetIfValid(p1);
 	if (v == NULL) return CMD_ERROR;
 
-	if (!CheckOwnership(v->owner)) return CMD_ERROR;
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
+
 	if (!v->IsInDepot()) return CMD_ERROR;
 	if (v->vehstatus & VS_CRASHED) return CMD_ERROR;
 

src/company_cmd.cpp

@@ -248,17 +248,17 @@ void GetNameOfOwner(Owner owner, TileIndex tile)
  * @param owner the owner of the thing to check.
  * @param tile  optional tile to get the right town.
  * @pre if tile == 0 then the owner can't be OWNER_TOWN.
- * @return true iff it's owned by the current company.
+ * @return A succeeded command iff it's owned by the current company, else a failed command.
  */
-bool CheckOwnership(Owner owner, TileIndex tile)
+CommandCost CheckOwnership(Owner owner, TileIndex tile)
 {
 	assert(owner < OWNER_END);
 	assert(owner != OWNER_TOWN || tile != 0);
 
-	if (owner == _current_company) return true;
+	if (owner == _current_company) return CommandCost();
-	_error_message = STR_ERROR_OWNED_BY;
+
 	GetNameOfOwner(owner, tile);
-	return false;
+	return_cmd_error(STR_ERROR_OWNED_BY);
 }
 
 /**

src/functions.h

@@ -24,7 +24,7 @@ void TileLoopClearHelper(TileIndex tile);
 bool CheckCompanyHasMoney(CommandCost &cost);
 void SubtractMoneyFromCompany(CommandCost cost);
 void SubtractMoneyFromCompanyFract(CompanyID company, CommandCost cost);
-bool CheckOwnership(Owner owner, TileIndex tile = 0);
+CommandCost CheckOwnership(Owner owner, TileIndex tile = 0);
 CommandCost CheckTileOwnership(TileIndex tile);
 
 /* misc functions */

src/order_cmd.cpp

@@ -468,7 +468,11 @@ CommandCost CmdInsertOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 	Order new_order(p2);
 
 	Vehicle *v = Vehicle::GetIfValid(veh);
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	/* Check if the inserted order is to the correct destination (owner, type),
 	 * and has the correct flags if any */
@@ -477,7 +481,11 @@ CommandCost CmdInsertOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 			const Station *st = Station::GetIfValid(new_order.GetDestination());
 			if (st == NULL) return CMD_ERROR;
 
-			if (st->owner != OWNER_NONE && !CheckOwnership(st->owner)) return CMD_ERROR;
+			if (st->owner != OWNER_NONE) {
+				CommandCost ret = CheckOwnership(st->owner);
+				ret.SetGlobalErrorMessage();
+				if (ret.Failed()) return ret;
+			}
 
 			if (!CanVehicleUseStation(v, st)) return_cmd_error(STR_ERROR_CAN_T_ADD_ORDER);
 			for (Vehicle *u = v->FirstShared(); u != NULL; u = u->NextShared()) {
@@ -521,15 +529,23 @@ CommandCost CmdInsertOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 				if (v->type == VEH_AIRCRAFT) {
 					const Station *st = Station::GetIfValid(new_order.GetDestination());
 
-					if (st == NULL || !CheckOwnership(st->owner) ||
+					if (st == NULL) return CMD_ERROR;
-							!CanVehicleUseStation(v, st) ||
+
-							st->GetAirportSpec()->nof_depots == 0) {
+					CommandCost ret = CheckOwnership(st->owner);
+					ret.SetGlobalErrorMessage();
+					if (ret.Failed()) return ret;
+
+					if (!CanVehicleUseStation(v, st) || st->GetAirportSpec()->nof_depots == 0) {
 						return CMD_ERROR;
 					}
 				} else {
 					const Depot *dp = Depot::GetIfValid(new_order.GetDestination());
 
-					if (dp == NULL || !CheckOwnership(GetTileOwner(dp->xy))) return CMD_ERROR;
+					if (dp == NULL) return CMD_ERROR;
+
+					CommandCost ret = CheckOwnership(GetTileOwner(dp->xy));
+					ret.SetGlobalErrorMessage();
+					if (ret.Failed()) return ret;
 
 					switch (v->type) {
 						case VEH_TRAIN:
@@ -565,14 +581,22 @@ CommandCost CmdInsertOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 			switch (v->type) {
 				default: return CMD_ERROR;
 
-				case VEH_TRAIN:
+				case VEH_TRAIN: {
 					if (!(wp->facilities & FACIL_TRAIN)) return_cmd_error(STR_ERROR_CAN_T_ADD_ORDER);
-					if (!CheckOwnership(wp->owner)) return CMD_ERROR;
+
+					CommandCost ret = CheckOwnership(wp->owner);
+					ret.SetGlobalErrorMessage();
+					if (ret.Failed()) return ret;
 					break;
+				}
 
 				case VEH_SHIP:
 					if (!(wp->facilities & FACIL_DOCK)) return_cmd_error(STR_ERROR_CAN_T_ADD_ORDER);
-					if (!CheckOwnership(wp->owner) && wp->owner != OWNER_NONE) return CMD_ERROR;
+					if (wp->owner != OWNER_NONE) {
+						CommandCost ret = CheckOwnership(wp->owner);
+						ret.SetGlobalErrorMessage();
+						if (ret.Failed()) return ret;
+					}
 					break;
 			}
 
@@ -729,7 +753,11 @@ CommandCost CmdDeleteOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 
 	Vehicle *v = Vehicle::GetIfValid(veh_id);
 
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	/* If we did not select an order, we maybe want to de-clone the orders */
 	if (sel_ord >= v->GetNumOrders())
@@ -795,10 +823,11 @@ CommandCost CmdSkipToOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 
 	Vehicle *v = Vehicle::GetIfValid(veh_id);
 
-	if (v == NULL || !CheckOwnership(v->owner) || sel_ord == v->cur_order_index ||
+	if (v == NULL || sel_ord == v->cur_order_index || sel_ord >= v->GetNumOrders() || v->GetNumOrders() < 2) return CMD_ERROR;
-			sel_ord >= v->GetNumOrders() || v->GetNumOrders() < 2) {
+
-		return CMD_ERROR;
+	CommandCost ret = CheckOwnership(v->owner);
-	}
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	if (flags & DC_EXEC) {
 		v->cur_order_index = sel_ord;
@@ -835,7 +864,11 @@ CommandCost CmdMoveOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 	VehicleOrderID target_order = GB(p2, 16, 16);
 
 	Vehicle *v = Vehicle::GetIfValid(veh);
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	/* Don't make senseless movements */
 	if (moving_order >= v->GetNumOrders() || target_order >= v->GetNumOrders() ||
@@ -916,7 +949,11 @@ CommandCost CmdModifyOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 	if (mof >= MOF_END) return CMD_ERROR;
 
 	Vehicle *v = Vehicle::GetIfValid(veh);
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	/* Is it a valid order? */
 	if (sel_ord >= v->GetNumOrders()) return CMD_ERROR;
@@ -1139,17 +1176,22 @@ CommandCost CmdCloneOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 	VehicleID veh_dst = GB(p1,  0, 16);
 
 	Vehicle *dst = Vehicle::GetIfValid(veh_dst);
+	if (dst == NULL) return CMD_ERROR;
 
-	if (dst == NULL || !CheckOwnership(dst->owner)) return CMD_ERROR;
+	CommandCost ret = CheckOwnership(dst->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	switch (p2) {
 		case CO_SHARE: {
 			Vehicle *src = Vehicle::GetIfValid(veh_src);
 
 			/* Sanity checks */
-			if (src == NULL || !CheckOwnership(src->owner) || dst->type != src->type || dst == src) {
+			if (src == NULL || dst->type != src->type || dst == src) return CMD_ERROR;
-				return CMD_ERROR;
+
-			}
+			CommandCost ret = CheckOwnership(src->owner);
+			ret.SetGlobalErrorMessage();
+			if (ret.Failed()) return ret;
 
 			/* Trucks can't share orders with busses (and visa versa) */
 			if (src->type == VEH_ROAD && RoadVehicle::From(src)->IsBus() != RoadVehicle::From(dst)->IsBus()) {
@@ -1188,9 +1230,11 @@ CommandCost CmdCloneOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 			Vehicle *src = Vehicle::GetIfValid(veh_src);
 
 			/* Sanity checks */
-			if (src == NULL || !CheckOwnership(src->owner) || dst->type != src->type || dst == src) {
+			if (src == NULL || dst->type != src->type || dst == src) return CMD_ERROR;
-				return CMD_ERROR;
+
-			}
+			CommandCost ret = CheckOwnership(src->owner);
+			ret.SetGlobalErrorMessage();
+			if (ret.Failed()) return ret;
 
 			/* Trucks can't copy all the orders from busses (and visa versa),
 			 * and neither can helicopters and aircarft. */
@@ -1264,7 +1308,11 @@ CommandCost CmdOrderRefit(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 	byte subtype  = GB(p2, 8, 8);
 
 	const Vehicle *v = Vehicle::GetIfValid(veh);
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	Order *order = v->GetOrder(order_number);
 	if (order == NULL) return CMD_ERROR;
@@ -1416,7 +1464,12 @@ CommandCost CmdRestoreOrderIndex(TileIndex tile, DoCommandFlag flags, uint32 p1,
 
 	Vehicle *v = Vehicle::GetIfValid(p1);
 	/* Check the vehicle type and ownership, and if the service interval and order are in range */
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
+
 	if (serv_int != GetServiceIntervalClamped(serv_int, v->owner) || cur_ord >= v->GetNumOrders()) return CMD_ERROR;
 
 	if (flags & DC_EXEC) {

src/road_cmd.cpp

@@ -131,7 +131,9 @@ CommandCost CheckAllowRemoveRoad(TileIndex tile, RoadBits remove, Owner owner, R
 	 * by a town */
 	if (owner != OWNER_TOWN) {
 		if (owner == OWNER_NONE) return CommandCost();
-		return CheckOwnership(owner) ? CommandCost() : CMD_ERROR;
+		CommandCost ret = CheckOwnership(owner);
+		ret.SetGlobalErrorMessage();
+		return ret;
 	}
 
 	if (!town_check) return CommandCost();
@@ -502,7 +504,11 @@ CommandCost CmdBuildRoad(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 							if (crossing) return_cmd_error(STR_ERROR_ONEWAY_ROADS_CAN_T_HAVE_JUNCTION);
 
 							Owner owner = GetRoadOwner(tile, ROADTYPE_ROAD);
-							if (owner != OWNER_NONE && !CheckOwnership(owner, tile)) return CMD_ERROR;
+							if (owner != OWNER_NONE) {
+								CommandCost ret = CheckOwnership(owner, tile);
+								ret.SetGlobalErrorMessage();
+								if (ret.Failed()) return ret;
+							}
 
 							CommandCost ret = EnsureNoVehicleOnGround(tile);
 							ret.SetGlobalErrorMessage();

src/roadveh_cmd.cpp

@@ -331,7 +331,11 @@ bool RoadVehicle::IsStoppedInDepot() const
 CommandCost CmdSellRoadVeh(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	RoadVehicle *v = RoadVehicle::GetIfValid(p1);
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	if (v->vehstatus & VS_CRASHED) return_cmd_error(STR_ERROR_CAN_T_SELL_DESTROYED_VEHICLE);
 
@@ -339,7 +343,7 @@ CommandCost CmdSellRoadVeh(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 		return_cmd_error(STR_ERROR_ROAD_VEHICLE_MUST_BE_STOPPED_INSIDE_DEPOT);
 	}
 
-	CommandCost ret(EXPENSES_NEW_VEHICLES, -v->value);
+	ret = CommandCost(EXPENSES_NEW_VEHICLES, -v->value);
 
 	if (flags & DC_EXEC) {
 		delete v;
@@ -406,7 +410,11 @@ CommandCost CmdSendRoadVehToDepot(TileIndex tile, DoCommandFlag flags, uint32 p1
 CommandCost CmdTurnRoadVeh(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	RoadVehicle *v = RoadVehicle::GetIfValid(p1);
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	if ((v->vehstatus & VS_STOPPED) ||
 			(v->vehstatus & VS_CRASHED) ||
@@ -1748,8 +1756,12 @@ CommandCost CmdRefitRoadVeh(TileIndex tile, DoCommandFlag flags, uint32 p1, uint
 	bool only_this = HasBit(p2, 16);
 
 	RoadVehicle *v = RoadVehicle::GetIfValid(p1);
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
 	if (!v->IsStoppedInDepot()) return_cmd_error(STR_ERROR_ROAD_VEHICLE_MUST_BE_STOPPED_INSIDE_DEPOT);
 	if (v->vehstatus & VS_CRASHED) return_cmd_error(STR_ERROR_CAN_T_REFIT_DESTROYED_VEHICLE);
 

src/ship_cmd.cpp

@@ -709,7 +709,11 @@ CommandCost CmdBuildShip(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 CommandCost CmdSellShip(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Ship *v = Ship::GetIfValid(p1);
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	if (v->vehstatus & VS_CRASHED) return_cmd_error(STR_ERROR_CAN_T_SELL_DESTROYED_VEHICLE);
 
@@ -717,7 +721,7 @@ CommandCost CmdSellShip(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p
 		return_cmd_error(STR_ERROR_SHIP_MUST_BE_STOPPED_IN_DEPOT);
 	}
 
-	CommandCost ret(EXPENSES_NEW_VEHICLES, -v->value);
+	ret = CommandCost(EXPENSES_NEW_VEHICLES, -v->value);
 
 	if (flags & DC_EXEC) {
 		delete v;
@@ -780,8 +784,12 @@ CommandCost CmdRefitShip(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 	byte new_subtype = GB(p2, 8, 8);
 
 	Ship *v = Ship::GetIfValid(p1);
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
 	if (!v->IsStoppedInDepot()) return_cmd_error(STR_ERROR_SHIP_MUST_BE_STOPPED_IN_DEPOT);
 	if (v->vehstatus & VS_CRASHED) return_cmd_error(STR_ERROR_CAN_T_REFIT_DESTROYED_VEHICLE);
 

src/station_cmd.cpp

@@ -865,8 +865,10 @@ static CommandCost CheckFlatLandRoadStop(TileArea tile_area, DoCommandFlag flags
 					Owner road_owner = GetRoadOwner(cur_tile, ROADTYPE_ROAD);
 					if (road_owner == OWNER_TOWN) {
 						if (!_settings_game.construction.road_stop_on_town_road) return_cmd_error(STR_ERROR_DRIVE_THROUGH_ON_TOWN_ROAD);
-					} else if (!_settings_game.construction.road_stop_on_competitor_road && road_owner != OWNER_NONE && !CheckOwnership(road_owner)) {
+					} else if (!_settings_game.construction.road_stop_on_competitor_road && road_owner != OWNER_NONE) {
-						return CMD_ERROR;
+						CommandCost ret = CheckOwnership(road_owner);
+						ret.SetGlobalErrorMessage();
+						if (ret.Failed()) return ret;
 					}
 					num_roadbits += CountBits(GetRoadBits(cur_tile, ROADTYPE_ROAD));
 				}
@@ -874,8 +876,10 @@ static CommandCost CheckFlatLandRoadStop(TileArea tile_area, DoCommandFlag flags
 				/* There is a tram, check if we can build road+tram stop over it. */
 				if (HasBit(cur_rts, ROADTYPE_TRAM)) {
 					Owner tram_owner = GetRoadOwner(cur_tile, ROADTYPE_TRAM);
-					if (!_settings_game.construction.road_stop_on_competitor_road && tram_owner != OWNER_NONE && !CheckOwnership(tram_owner)) {
+					if (!_settings_game.construction.road_stop_on_competitor_road && tram_owner != OWNER_NONE) {
-						return CMD_ERROR;
+						CommandCost ret = CheckOwnership(tram_owner);
+						ret.SetGlobalErrorMessage();
+						if (ret.Failed()) return ret;
 					}
 					num_roadbits += CountBits(GetRoadBits(cur_tile, ROADTYPE_TRAM));
 				}
@@ -1383,7 +1387,14 @@ CommandCost RemoveFromRailBaseStation(TileArea ta, SmallVector<T *, 4> &affected
 		/* Check ownership of station */
 		T *st = T::GetByTile(tile);
 		if (st == NULL) continue;
-		if (_current_company != OWNER_WATER && !CheckOwnership(st->owner)) continue;
+
+		if (_current_company != OWNER_WATER) {
+			CommandCost ret = CheckOwnership(st->owner);
+			if (ret.Failed()) {
+				ret.SetGlobalErrorMessage();
+				continue;
+			}
+		}
 
 		/* Do not allow removing from stations if non-uniform stations are not enabled
 		 * The check must be here to give correct error message
@@ -1529,7 +1540,11 @@ template <class T>
 CommandCost RemoveRailStation(T *st, DoCommandFlag flags)
 {
 	/* Current company owns the station? */
-	if (_current_company != OWNER_WATER && !CheckOwnership(st->owner)) return CMD_ERROR;
+	if (_current_company != OWNER_WATER) {
+		CommandCost ret = CheckOwnership(st->owner);
+		ret.SetGlobalErrorMessage();
+		if (ret.Failed()) return ret;
+	}
 
 	/* determine width and height of platforms */
 	TileArea ta = st->train_station;
@@ -1829,8 +1844,10 @@ static CommandCost RemoveRoadStop(TileIndex tile, DoCommandFlag flags)
 {
 	Station *st = Station::GetByTile(tile);
 
-	if (_current_company != OWNER_WATER && !CheckOwnership(st->owner)) {
+	if (_current_company != OWNER_WATER) {
-		return CMD_ERROR;
+		CommandCost ret = CheckOwnership(st->owner);
+		ret.SetGlobalErrorMessage();
+		if (ret.Failed()) return ret;
 	}
 
 	bool is_truck = IsTruckStop(tile);
@@ -2241,8 +2258,10 @@ static CommandCost RemoveAirport(TileIndex tile, DoCommandFlag flags)
 {
 	Station *st = Station::GetByTile(tile);
 
-	if (_current_company != OWNER_WATER && !CheckOwnership(st->owner)) {
+	if (_current_company != OWNER_WATER) {
-		return CMD_ERROR;
+		CommandCost ret = CheckOwnership(st->owner);
+		ret.SetGlobalErrorMessage();
+		if (ret.Failed()) return ret;
 	}
 
 	tile = st->airport.tile;
@@ -2456,12 +2475,14 @@ CommandCost CmdBuildDock(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 static CommandCost RemoveDock(TileIndex tile, DoCommandFlag flags)
 {
 	Station *st = Station::GetByTile(tile);
-	if (!CheckOwnership(st->owner)) return CMD_ERROR;
+	CommandCost ret = CheckOwnership(st->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	TileIndex tile1 = st->dock_tile;
 	TileIndex tile2 = tile1 + TileOffsByDiagDir(GetDockDirection(tile1));
 
-	CommandCost ret = EnsureNoVehicleOnGround(tile1);
+	ret = EnsureNoVehicleOnGround(tile1);
 	if (ret.Succeeded()) ret = EnsureNoVehicleOnGround(tile2);
 	ret.SetGlobalErrorMessage();
 	if (ret.Failed()) return ret;
@@ -3194,7 +3215,11 @@ static bool IsUniqueStationName(const char *name)
 CommandCost CmdRenameStation(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Station *st = Station::GetIfValid(p1);
-	if (st == NULL || !CheckOwnership(st->owner)) return CMD_ERROR;
+	if (st == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(st->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	bool reset = StrEmpty(text);
 
@@ -3441,7 +3466,7 @@ static bool CanRemoveRoadWithStop(TileIndex tile, DoCommandFlag flags)
 	if (HasBit(rts, ROADTYPE_ROAD)) road_owner = GetRoadOwner(tile, ROADTYPE_ROAD);
 	if (HasBit(rts, ROADTYPE_TRAM)) tram_owner = GetRoadOwner(tile, ROADTYPE_TRAM);
 
-	if ((road_owner != OWNER_TOWN && !CheckOwnership(road_owner)) || !CheckOwnership(tram_owner)) return false;
+	if ((road_owner != OWNER_TOWN && CheckOwnership(road_owner).Failed()) || CheckOwnership(tram_owner).Failed()) return false;
 
 	return road_owner != OWNER_TOWN || CheckAllowRemoveRoad(tile, GetAnyRoadBits(tile, ROADTYPE_ROAD), OWNER_TOWN, ROADTYPE_ROAD, flags).Succeeded();
 }

src/timetable_cmd.cpp

@@ -68,7 +68,11 @@ CommandCost CmdChangeTimetable(TileIndex tile, DoCommandFlag flags, uint32 p1, u
 	VehicleID veh = GB(p1, 0, 16);
 
 	Vehicle *v = Vehicle::GetIfValid(veh);
-	if (v == NULL || !CheckOwnership(v->owner) || !v->IsPrimaryVehicle()) return CMD_ERROR;
+	if (v == NULL || !v->IsPrimaryVehicle()) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	VehicleOrderID order_number = GB(p1, 16, 8);
 	Order *order = v->GetOrder(order_number);
@@ -128,7 +132,11 @@ CommandCost CmdSetVehicleOnTime(TileIndex tile, DoCommandFlag flags, uint32 p1,
 	VehicleID veh = GB(p1, 0, 16);
 
 	Vehicle *v = Vehicle::GetIfValid(veh);
-	if (v == NULL || !CheckOwnership(v->owner) || !v->IsPrimaryVehicle()) return CMD_ERROR;
+	if (v == NULL || !v->IsPrimaryVehicle()) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	if (flags & DC_EXEC) {
 		v->lateness_counter = 0;
@@ -150,7 +158,11 @@ CommandCost CmdSetTimetableStart(TileIndex tile, DoCommandFlag flags, uint32 p1,
 	if (!_settings_game.order.timetabling) return CMD_ERROR;
 
 	Vehicle *v = Vehicle::GetIfValid(GB(p1, 0, 16));
-	if (v == NULL || !CheckOwnership(v->owner) || !v->IsPrimaryVehicle()) return CMD_ERROR;
+	if (v == NULL || !v->IsPrimaryVehicle()) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	/* Don't let a timetable start more than 15 years into the future or 1 year in the past. */
 	Date start_date = (Date)p2;
@@ -190,7 +202,11 @@ CommandCost CmdAutofillTimetable(TileIndex tile, DoCommandFlag flags, uint32 p1,
 	VehicleID veh = GB(p1, 0, 16);
 
 	Vehicle *v = Vehicle::GetIfValid(veh);
-	if (v == NULL || !CheckOwnership(v->owner) || !v->IsPrimaryVehicle()) return CMD_ERROR;
+	if (v == NULL || !v->IsPrimaryVehicle()) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	if (flags & DC_EXEC) {
 		if (HasBit(p2, 0)) {

src/train_cmd.cpp

@@ -1169,7 +1169,11 @@ CommandCost CmdMoveRailVehicle(TileIndex tile, DoCommandFlag flags, uint32 p1, u
 	bool move_chain = HasBit(p2, 0);
 
 	Train *src = Train::GetIfValid(s);
-	if (src == NULL || !CheckOwnership(src->owner)) return CMD_ERROR;
+	if (src == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(src->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	/* Do not allow moving crashed vehicles inside the depot, it is likely to cause asserts later */
 	if (src->vehstatus & VS_CRASHED) return CMD_ERROR;
@@ -1180,7 +1184,11 @@ CommandCost CmdMoveRailVehicle(TileIndex tile, DoCommandFlag flags, uint32 p1, u
 		dst = src->IsEngine() ? NULL : FindGoodVehiclePos(src);
 	} else {
 		dst = Train::GetIfValid(d);
-		if (dst == NULL || !CheckOwnership(dst->owner)) return CMD_ERROR;
+		if (dst == NULL) return CMD_ERROR;
+
+		CommandCost ret = CheckOwnership(dst->owner);
+		ret.SetGlobalErrorMessage();
+		if (ret.Failed()) return ret;
 
 		/* Do not allow appending to crashed vehicles, too */
 		if (dst->vehstatus & VS_CRASHED) return CMD_ERROR;
@@ -1342,7 +1350,11 @@ CommandCost CmdSellRailWagon(TileIndex tile, DoCommandFlag flags, uint32 p1, uin
 	Window *w = NULL;
 
 	Train *v = Train::GetIfValid(p1);
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	/* Sell a chain of vehicles or not? */
 	bool sell_chain = HasBit(p2, 0);
@@ -1372,7 +1384,7 @@ CommandCost CmdSellRailWagon(TileIndex tile, DoCommandFlag flags, uint32 p1, uin
 	ArrangeTrains(&sell_head, NULL, &new_head, v, sell_chain);
 
 	/* We don't need to validate the second train; it's going to be sold. */
-	CommandCost ret = ValidateTrains(NULL, NULL, first, new_head);
+	ret = ValidateTrains(NULL, NULL, first, new_head);
 	if (ret.Failed()) {
 		/* Restore the train we had. */
 		RestoreTrainBackup(original);
@@ -1815,7 +1827,11 @@ static void ReverseTrainDirection(Train *v)
 CommandCost CmdReverseTrainDirection(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Train *v = Train::GetIfValid(p1);
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	if (p2 != 0) {
 		/* turn a single unit around */
@@ -1882,7 +1898,12 @@ CommandCost CmdReverseTrainDirection(TileIndex tile, DoCommandFlag flags, uint32
 CommandCost CmdForceTrainProceed(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Train *t = Train::GetIfValid(p1);
-	if (t == NULL || !CheckOwnership(t->owner)) return CMD_ERROR;
+	if (t == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(t->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
+
 
 	if (flags & DC_EXEC) {
 		/* If we are forced to proceed, cancel that order.
@@ -1915,7 +1936,11 @@ CommandCost CmdRefitRailVehicle(TileIndex tile, DoCommandFlag flags, uint32 p1,
 	bool only_this = HasBit(p2, 16);
 
 	Train *v = Train::GetIfValid(p1);
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	if (!v->IsStoppedInDepot()) return_cmd_error(STR_TRAIN_MUST_BE_STOPPED);
 	if (v->vehstatus & VS_CRASHED) return_cmd_error(STR_ERROR_CAN_T_REFIT_DESTROYED_VEHICLE);

src/tunnelbridge_cmd.cpp

@@ -613,12 +613,18 @@ static inline CommandCost CheckAllowRemoveTunnelBridge(TileIndex tile)
 			if (road_owner == OWNER_NONE || road_owner == OWNER_TOWN) road_owner = _current_company;
 			if (tram_owner == OWNER_NONE) tram_owner = _current_company;
 
-			return (CheckOwnership(road_owner, tile) && CheckOwnership(tram_owner, tile)) ? CommandCost() : CMD_ERROR;
+			CommandCost ret = CheckOwnership(road_owner, tile);
+			if (ret.Succeeded()) ret = CheckOwnership(tram_owner, tile);
+			ret.SetGlobalErrorMessage();
+			return ret;
 		}
 
 		case TRANSPORT_RAIL:
-		case TRANSPORT_WATER:
+		case TRANSPORT_WATER: {
-			return CheckOwnership(GetTileOwner(tile)) ? CommandCost() : CMD_ERROR;
+			CommandCost ret = CheckOwnership(GetTileOwner(tile));
+			ret.SetGlobalErrorMessage();
+			return ret;
+		}
 
 		default: NOT_REACHED();
 	}

src/vehicle.cpp

@@ -1665,7 +1665,10 @@ void Vehicle::HandleLoading(bool mode)
 
 CommandCost Vehicle::SendToDepot(DoCommandFlag flags, DepotCommand command)
 {
-	if (!CheckOwnership(this->owner)) return CMD_ERROR;
+	CommandCost ret = CheckOwnership(this->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
+
 	if (this->vehstatus & VS_CRASHED) return CMD_ERROR;
 	if (this->IsStoppedInDepot()) return CMD_ERROR;
 

src/vehicle_cmd.cpp

@@ -74,7 +74,11 @@ CommandCost CmdStartStopVehicle(TileIndex tile, DoCommandFlag flags, uint32 p1,
 	if ((flags & DC_AUTOREPLACE) == 0) SetBit(p2, 0);
 
 	Vehicle *v = Vehicle::GetIfValid(p1);
-	if (v == NULL || !CheckOwnership(v->owner) || !v->IsPrimaryVehicle()) return CMD_ERROR;
+	if (v == NULL || !v->IsPrimaryVehicle()) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	switch (v->type) {
 		case VEH_TRAIN:
@@ -406,7 +410,9 @@ CommandCost CmdCloneVehicle(TileIndex tile, DoCommandFlag flags, uint32 p1, uint
 	 * w_rear is the rear end of the cloned train. It's used to add more cars and is only used by trains
 	 */
 
-	if (!CheckOwnership(v->owner)) return CMD_ERROR;
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	if (v->type == VEH_TRAIN && (!Train::From(v)->IsFrontEngine() || Train::From(v)->crash_anim_pos >= 4400)) return CMD_ERROR;
 
@@ -607,7 +613,11 @@ CommandCost SendAllVehiclesToDepot(VehicleType type, DoCommandFlag flags, bool s
 CommandCost CmdRenameVehicle(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Vehicle *v = Vehicle::GetIfValid(p1);
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	bool reset = StrEmpty(text);
 
@@ -638,7 +648,11 @@ CommandCost CmdRenameVehicle(TileIndex tile, DoCommandFlag flags, uint32 p1, uin
 CommandCost CmdChangeServiceInt(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Vehicle *v = Vehicle::GetIfValid(p1);
-	if (v == NULL || !CheckOwnership(v->owner)) return CMD_ERROR;
+	if (v == NULL) return CMD_ERROR;
+
+	CommandCost ret = CheckOwnership(v->owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	uint16 serv_int = GetServiceIntervalClamped(p2, v->owner); // Double check the service interval from the user-input
 	if (serv_int != p2) return CMD_ERROR;

src/waypoint_cmd.cpp

@@ -178,9 +178,11 @@ static CommandCost IsValidTileForWaypoint(TileIndex tile, Axis axis, StationID *
 	if (GetAxisForNewWaypoint(tile) != axis) return_cmd_error(STR_ERROR_NO_SUITABLE_RAILROAD_TRACK);
 
 	Owner owner = GetTileOwner(tile);
-	if (!CheckOwnership(owner)) return CMD_ERROR;
+	CommandCost ret = CheckOwnership(owner);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
-	CommandCost ret = EnsureNoVehicleOnGround(tile);
+	ret = EnsureNoVehicleOnGround(tile);
 	ret.SetGlobalErrorMessage();
 	if (ret.Failed()) return ret;
 
@@ -445,7 +447,13 @@ static bool IsUniqueWaypointName(const char *name)
 CommandCost CmdRenameWaypoint(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Waypoint *wp = Waypoint::GetIfValid(p1);
-	if (wp == NULL || !(CheckOwnership(wp->owner) || wp->owner == OWNER_NONE)) return CMD_ERROR;
+	if (wp == NULL) return CMD_ERROR;
+
+	if (wp->owner != OWNER_NONE) {
+		CommandCost ret = CheckOwnership(wp->owner);
+		ret.SetGlobalErrorMessage();
+		if (ret.Failed()) return ret;
+	}
 
 	bool reset = StrEmpty(text);