Fix #14974: too many dodgems not handled correctly

Properly check if all vehicles have been created, and clean them up properly if not.

src/openrct2/ride/Ride.cpp

@@ -3087,9 +3087,15 @@ static Vehicle* vehicle_create_car(
         vehicle->update_flags = 0;
 
         CoordsXY chosenLoc;
+        auto numAttempts = 0;
         // loc_6DDD26:
         do
         {
+            numAttempts++;
+            // This can happen when trying to spawn dozens of cars in a tiny area.
+            if (numAttempts > 10000)
+                return nullptr;
+
             vehicle->sprite_direction = scenario_rand() & 0x1E;
             chosenLoc.y = dodgemPos.y + (scenario_rand() & 0xFF);
             chosenLoc.x = dodgemPos.x + (scenario_rand() & 0xFF);
@@ -3233,15 +3239,16 @@ static train_ref vehicle_create_train(
     return train;
 }
 
-static void vehicle_create_trains(ride_id_t rideIndex, const CoordsXYZ& trainsPos, TrackElement* trackElement)
+static bool vehicle_create_trains(ride_id_t rideIndex, const CoordsXYZ& trainsPos, TrackElement* trackElement)
 {
     auto ride = get_ride(rideIndex);
     if (ride == nullptr)
-        return;
+        return false;
 
     train_ref firstTrain = {};
     train_ref lastTrain = {};
     int32_t remainingDistance = 0;
+    bool allTrainsCreated = true;
 
     for (int32_t vehicleIndex = 0; vehicleIndex < ride->num_vehicles; vehicleIndex++)
     {
@@ -3251,7 +3258,10 @@ static void vehicle_create_trains(ride_id_t rideIndex, const CoordsXYZ& trainsPo
         }
         train_ref train = vehicle_create_train(rideIndex, trainsPos, vehicleIndex, &remainingDistance, trackElement);
         if (train.head == nullptr || train.tail == nullptr)
+        {
+            allTrainsCreated = false;
             continue;
+        }
 
         if (vehicleIndex == 0)
         {
@@ -3280,6 +3290,8 @@ static void vehicle_create_trains(ride_id_t rideIndex, const CoordsXYZ& trainsPo
         firstTrain.head->prev_vehicle_on_ride = lastTrain.tail->sprite_index;
     if (firstTrain.head != nullptr)
         lastTrain.tail->next_vehicle_on_ride = firstTrain.head->sprite_index;
+
+    return allTrainsCreated;
 }
 
 /**
@@ -3389,7 +3401,14 @@ bool Ride::CreateVehicles(const CoordsXYE& element, bool isApplying)
         direction = trackElement->GetDirection();
     }
 
-    vehicle_create_trains(id, vehiclePos, trackElement);
+    if (!vehicle_create_trains(id, vehiclePos, trackElement))
+    {
+        // This flag is needed for Ride::RemoveVehicles()
+        lifecycle_flags |= RIDE_LIFECYCLE_ON_TRACK;
+        RemoveVehicles();
+        gGameCommandErrorText = STR_UNABLE_TO_CREATE_ENOUGH_VEHICLES;
+        return false;
+    }
     // return true;
 
     // Initialise station departs

src/openrct2/ride/Ride.h

@@ -466,6 +466,8 @@ public:
 
     uint8_t GetNumShelteredSections() const;
     void IncreaseNumShelteredSections();
+
+    void RemoveVehicles();
 };
 
 #pragma pack(push, 1)

src/openrct2/ride/RideConstruction.cpp

@@ -40,6 +40,7 @@
 #include "RideData.h"
 #include "Track.h"
 #include "TrackData.h"
+#include "TrainManager.h"
 #include "Vehicle.h"
 
 bool gGotoStartPlacementMode = false;
@@ -173,16 +174,16 @@ static void ride_remove_cable_lift(Ride* ride)
  *
  *  rct2: 0x006DD506
  */
-static void ride_remove_vehicles(Ride* ride)
+void Ride::RemoveVehicles()
 {
-    if (ride->lifecycle_flags & RIDE_LIFECYCLE_ON_TRACK)
+    if (lifecycle_flags & RIDE_LIFECYCLE_ON_TRACK)
     {
-        ride->lifecycle_flags &= ~RIDE_LIFECYCLE_ON_TRACK;
-        ride->lifecycle_flags &= ~(RIDE_LIFECYCLE_TEST_IN_PROGRESS | RIDE_LIFECYCLE_HAS_STALLED_VEHICLE);
+        lifecycle_flags &= ~RIDE_LIFECYCLE_ON_TRACK;
+        lifecycle_flags &= ~(RIDE_LIFECYCLE_TEST_IN_PROGRESS | RIDE_LIFECYCLE_HAS_STALLED_VEHICLE);
 
         for (size_t i = 0; i <= MAX_VEHICLES_PER_RIDE; i++)
         {
-            uint16_t spriteIndex = ride->vehicles[i];
+            uint16_t spriteIndex = vehicles[i];
             while (spriteIndex != SPRITE_INDEX_NULL)
             {
                 Vehicle* vehicle = GetEntity<Vehicle>(spriteIndex);
@@ -195,11 +196,21 @@ static void ride_remove_vehicles(Ride* ride)
                 sprite_remove(vehicle);
             }
 
-            ride->vehicles[i] = SPRITE_INDEX_NULL;
+            vehicles[i] = SPRITE_INDEX_NULL;
         }
 
         for (size_t i = 0; i < MAX_STATIONS; i++)
-            ride->stations[i].TrainAtStation = RideStation::NO_TRAIN;
+            stations[i].TrainAtStation = RideStation::NO_TRAIN;
+
+        // Also clean up orphaned vehicles for good measure.
+        for (auto* vehicle : TrainManager::View())
+        {
+            if (vehicle->ride == id)
+            {
+                vehicle->Invalidate();
+                sprite_remove(vehicle);
+            }
+        }
     }
 }
 
@@ -223,7 +234,7 @@ void ride_clear_for_construction(Ride* ride)
     }
 
     ride_remove_cable_lift(ride);
-    ride_remove_vehicles(ride);
+    ride->RemoveVehicles();
     ride_clear_blocked_tiles(ride);
 
     auto w = window_find_by_number(WC_RIDE, ride->id);