Function DeleteLastWagon

src/train_cmd.cpp:3635–3708

* Deletes/Clears the last wagon of a crashed train. It takes the engine of the * train, then goes to the last wagon and deletes that. Each call to this function * will remove the last wagon of a crashed train. If this wagon was on a crossing, * or inside a tunnel/bridge, recalculate the signals as they might need updating * @param v the Vehicle of which last wagon is to be removed */

 * @param v the Vehicle of which last wagon is to be removed
 */
static void DeleteLastWagon(Train *v)
{
	Train *first = v->First();

	/* Go to the last wagon and delete the link pointing there
	 * new_last is then the one-before-last wagon, and v the last
	 * one which will physically be removed */
	Train *new_last = v;
	for (; v->Next() != nullptr; v = v->Next()) new_last = v;
	new_last->SetNext(nullptr);

	if (first != v) {
		/* Recalculate cached train properties */
		first->ConsistChanged(CCF_ARRANGE);
		/* Update the depot window if the first vehicle is in depot -
		 * if v == first, then it is updated in PreDestructor() */
		if (first->track == TRACK_BIT_DEPOT) {
			SetWindowDirty(WC_VEHICLE_DEPOT, first->tile);
		}
		v->last_station_visited = first->last_station_visited; // for PreDestructor
	}

	/* 'v' shouldn't be accessed after it has been deleted */
	TrackBits trackbits = v->track;
	TileIndex tile = v->tile;
	Owner owner = v->owner;

	delete v;
	v = nullptr; // make sure nobody will try to read 'v' anymore

	if (trackbits == TRACK_BIT_WORMHOLE) {
		/* Vehicle is inside a wormhole, v->track contains no useful value then. */
		trackbits = DiagDirToDiagTrackBits(GetTunnelBridgeDirection(tile));
	}

	Track track = TrackBitsToTrack(trackbits);
	if (HasReservedTracks(tile, trackbits)) {
		UnreserveRailTrack(tile, track);

		/* If there are still crashed vehicles on the tile, give the track reservation to them */
		TrackBits remaining_trackbits = TRACK_BIT_NONE;
		for (const Vehicle *u : VehiclesOnTile(tile)) {
			if (u->type != VEH_TRAIN || !u->vehstatus.Test(VehState::Crashed)) continue;
			TrackBits train_tbits = Train::From(u)->track;
			if (train_tbits == TRACK_BIT_WORMHOLE) {
				/* Vehicle is inside a wormhole, u->track contains no useful value then. */
				remaining_trackbits |= DiagDirToDiagTrackBits(GetTunnelBridgeDirection(u->tile));
			} else if (train_tbits != TRACK_BIT_DEPOT) {
				remaining_trackbits |= train_tbits;
			}
		}

		/* It is important that these two are the first in the loop, as reservation cannot deal with every trackbit combination */
		assert(TRACK_BEGIN == TRACK_X && TRACK_Y == TRACK_BEGIN + 1);
		for (Track t : SetTrackBitIterator(remaining_trackbits)) TryReserveRailTrack(tile, t);
	}

	/* check if the wagon was on a road/rail-crossing */