Codechange: Do not use a mutable global to return calculated VarAction2 results.

src/newgrf_engine.cpp

@@ -998,14 +998,14 @@ static uint32_t VehicleGetVariable(Vehicle *v, const VehicleScopeResolver *objec
 }
 
 
-/* virtual */ const SpriteGroup *VehicleResolverObject::ResolveReal(const RealSpriteGroup &group) const
+/* virtual */ ResolverResult VehicleResolverObject::ResolveReal(const RealSpriteGroup &group) const
 {
 	const Vehicle *v = this->self_scope.v;
 
 	if (v == nullptr) {
 		if (!group.loading.empty()) return group.loading[0];
 		if (!group.loaded.empty()) return group.loaded[0];
-		return nullptr;
+		return std::monostate{};
 	}
 
 	const Order &order = v->First()->current_order;
@@ -1014,7 +1014,7 @@ static uint32_t VehicleGetVariable(Vehicle *v, const VehicleScopeResolver *objec
 
 	uint totalsets = static_cast<uint>(in_motion ? group.loaded.size() : group.loading.size());
 
-	if (totalsets == 0) return nullptr;
+	if (totalsets == 0) return std::monostate{};
 
 	uint set = (v->cargo.StoredCount() * totalsets) / std::max<uint16_t>(1u, v->cargo_cap);
 	set = std::min(set, totalsets - 1);

src/newgrf_engine.h

@@ -64,7 +64,7 @@ struct VehicleResolverObject : public SpecializedResolverObject<VehicleRandomTri
 
 	ScopeResolver *GetScope(VarSpriteGroupScope scope = VSG_SCOPE_SELF, uint8_t relative = 0) override;
 
-	const SpriteGroup *ResolveReal(const RealSpriteGroup &group) const override;
+	ResolverResult ResolveReal(const RealSpriteGroup &group) const override;
 
 	GrfSpecFeature GetFeature() const override;
 	uint32_t GetDebugID() const override;

src/newgrf_profiling.cpp

@@ -60,20 +60,28 @@ void NewGRFProfiler::BeginResolve(const ResolverObject &resolver)
 /**
  * Capture the completion of a sprite group resolution.
  */
-void NewGRFProfiler::EndResolve(const SpriteGroup *result)
+void NewGRFProfiler::EndResolve(const ResolverResult &result)
 {
 	using namespace std::chrono;
 	this->cur_call.time = (uint32_t)time_point_cast<microseconds>(high_resolution_clock::now()).time_since_epoch().count() - this->cur_call.time;
 
-	if (result == nullptr) {
+	struct visitor {
-		this->cur_call.result = 0;
+		uint32_t operator()(std::monostate)
-	} else if (result->type == SGT_CALLBACK) {
+		{
-		this->cur_call.result = static_cast<const CallbackResultSpriteGroup *>(result)->result;
+			return 0;
-	} else if (result->type == SGT_RESULT) {
-		this->cur_call.result = GetSpriteLocalID(static_cast<const ResultSpriteGroup *>(result)->sprite);
-	} else {
-		this->cur_call.result = result->nfo_line;
 		}
+		uint32_t operator()(CallbackResult cb_result)
+		{
+			return cb_result;
+		}
+		uint32_t operator()(const SpriteGroup *group)
+		{
+			if (group == nullptr) return 0;
+			if (group->type != SGT_RESULT) return group->nfo_line;
+			return GetSpriteLocalID(static_cast<const ResultSpriteGroup *>(group)->sprite);
+		}
+	};
+	this->cur_call.result = std::visit(visitor{}, result);
 
 	this->calls.push_back(this->cur_call);
 }

src/newgrf_profiling.h

@@ -24,7 +24,7 @@ struct NewGRFProfiler {
 	~NewGRFProfiler();
 
 	void BeginResolve(const ResolverObject &resolver);
-	void EndResolve(const SpriteGroup *result);
+	void EndResolve(const ResolverResult &result);
 	void RecursiveResolve();
 
 	void Start();

src/newgrf_spritegroup.cpp

@@ -31,9 +31,9 @@ TemporaryStorageArray<int32_t, 0x110> _temp_store;
  * @param top_level true if this is a top-level SpriteGroup, false if used nested in another SpriteGroup.
  * @return the resolved group
  */
-/* static */ const SpriteGroup *SpriteGroup::Resolve(const SpriteGroup *group, ResolverObject &object, bool top_level)
+/* static */ ResolverResult SpriteGroup::Resolve(const SpriteGroup *group, ResolverObject &object, bool top_level)
 {
-	if (group == nullptr) return nullptr;
+	if (group == nullptr) return std::monostate{};
 
 	const GRFFile *grf = object.grffile;
 	auto profiler = std::ranges::find(_newgrf_profilers, grf, &NewGRFProfiler::grffile);
@@ -44,7 +44,7 @@ TemporaryStorageArray<int32_t, 0x110> _temp_store;
 	} else if (top_level) {
 		profiler->BeginResolve(object);
 		_temp_store.ClearChanges();
-		const SpriteGroup *result = group->Resolve(object);
+		auto result = group->Resolve(object);
 		profiler->EndResolve(result);
 		return result;
 	} else {
@@ -120,12 +120,12 @@ static inline uint32_t GetVariable(const ResolverObject &object, ScopeResolver *
  * @param group Group to get.
  * @return The available sprite group.
  */
-/* virtual */ const SpriteGroup *ResolverObject::ResolveReal(const RealSpriteGroup &group) const
+/* virtual */ ResolverResult ResolverObject::ResolveReal(const RealSpriteGroup &group) const
 {
 	if (!group.loaded.empty()) return group.loaded[0];
 	if (!group.loading.empty()) return group.loading[0];
 
-	return nullptr;
+	return std::monostate{};
 }
 
 /**
@@ -185,7 +185,7 @@ static bool RangeHighComparator(const DeterministicSpriteGroupRange &range, uint
 	return range.high < value;
 }
 
-const SpriteGroup *DeterministicSpriteGroup::Resolve(ResolverObject &object) const
+/* virtual */ ResolverResult DeterministicSpriteGroup::Resolve(ResolverObject &object) const
 {
 	uint32_t last_value = 0;
 	uint32_t value = 0;
@@ -196,13 +196,9 @@ const SpriteGroup *DeterministicSpriteGroup::Resolve(ResolverObject &object) con
 		/* Try to get the variable. We shall assume it is available, unless told otherwise. */
 		bool available = true;
 		if (adjust.variable == 0x7E) {
-			const SpriteGroup *subgroup = SpriteGroup::Resolve(adjust.subroutine, object, false);
+			auto subgroup = SpriteGroup::Resolve(adjust.subroutine, object, false);
-			if (subgroup == nullptr) {
+			auto *subvalue = std::get_if<CallbackResult>(&subgroup);
-				value = UINT16_MAX;
+			value = subvalue != nullptr ? *subvalue : UINT16_MAX;
-			} else {
-				value = subgroup->GetCallbackResult();
-				if (value == CALLBACK_FAILED) value = UINT16_MAX;
-			}
 
 			/* Note: 'last_value' and 'reseed' are shared between the main chain and the procedure */
 		} else if (adjust.variable == 0x7B) {
@@ -230,9 +226,7 @@ const SpriteGroup *DeterministicSpriteGroup::Resolve(ResolverObject &object) con
 
 	if (this->calculated_result) {
 		/* nvar == 0 is a special case -- we turn our value into a callback result */
-		static CallbackResultSpriteGroup nvarzero(0);
+		return static_cast<CallbackResult>(GB(value, 0, 15));
-		nvarzero.result = GB(value, 0, 15);
-		return &nvarzero;
 	}
 
 	if (this->ranges.size() > 4) {
@@ -253,7 +247,7 @@ const SpriteGroup *DeterministicSpriteGroup::Resolve(ResolverObject &object) con
 }
 
 
-const SpriteGroup *RandomizedSpriteGroup::Resolve(ResolverObject &object) const
+/* virtual */ ResolverResult RandomizedSpriteGroup::Resolve(ResolverObject &object) const
 {
 	ScopeResolver *scope = object.GetScope(this->var_scope, this->count);
 	if (object.callback == CBID_RANDOM_TRIGGER) {
@@ -273,8 +267,12 @@ const SpriteGroup *RandomizedSpriteGroup::Resolve(ResolverObject &object) const
 	return SpriteGroup::Resolve(this->groups[index], object, false);
 }
 
+/* virtual */ ResolverResult CallbackResultSpriteGroup::Resolve(ResolverObject &) const
+{
+	return this->result;
+}
 
-const SpriteGroup *RealSpriteGroup::Resolve(ResolverObject &object) const
+/* virtual */ ResolverResult RealSpriteGroup::Resolve(ResolverObject &object) const
 {
 	return object.ResolveReal(*this);
 }

src/newgrf_spritegroup.h

@@ -46,6 +46,15 @@ enum SpriteGroupType : uint8_t {
 
 struct SpriteGroup;
 struct ResolverObject;
+using CallbackResult = uint16_t;
+
+/**
+ * Result of resolving sprite groups:
+ * - std::monostate: Failure.
+ * - CallbackResult: Callback result.
+ * - SpriteGroup: ResultSpriteGroup, TileLayoutSpriteGroup, IndustryProductionSpriteGroup
+ */
+using ResolverResult = std::variant<std::monostate, CallbackResult, const SpriteGroup *>;
 
 /* SPRITE_WIDTH is 24. ECS has roughly 30 sprite groups per real sprite.
  * Adding an 'extra' margin would be assuming 64 sprite groups per real
@@ -59,7 +68,7 @@ struct SpriteGroup : SpriteGroupPool::PoolItem<&_spritegroup_pool> {
 protected:
 	SpriteGroup(SpriteGroupType type) : type(type) {}
 	/** Base sprite group resolver */
-	virtual const SpriteGroup *Resolve([[maybe_unused]] ResolverObject &object) const { return this; };
+	virtual ResolverResult Resolve([[maybe_unused]] ResolverObject &object) const { return this; };
 
 public:
 	virtual ~SpriteGroup() = default;
@@ -67,9 +76,7 @@ public:
 	uint32_t nfo_line = 0;
 	SpriteGroupType type{};
 
-	virtual uint16_t GetCallbackResult() const { return CALLBACK_FAILED; }
+	static ResolverResult Resolve(const SpriteGroup *group, ResolverObject &object, bool top_level = true);
-
-	static const SpriteGroup *Resolve(const SpriteGroup *group, ResolverObject &object, bool top_level = true);
 };
 
 
@@ -89,7 +96,7 @@ struct RealSpriteGroup : SpriteGroup {
 	std::vector<const SpriteGroup *> loading{}; ///< List of loading groups (can be SpriteIDs or Callback results)
 
 protected:
-	const SpriteGroup *Resolve(ResolverObject &object) const override;
+	ResolverResult Resolve(ResolverObject &object) const override;
 };
 
 /* Shared by deterministic and random groups. */
@@ -178,7 +185,7 @@ struct DeterministicSpriteGroup : SpriteGroup {
 	const SpriteGroup *error_group = nullptr; // was first range, before sorting ranges
 
 protected:
-	const SpriteGroup *Resolve(ResolverObject &object) const override;
+	ResolverResult Resolve(ResolverObject &object) const override;
 };
 
 enum RandomizedSpriteGroupCompareMode : uint8_t {
@@ -200,7 +207,7 @@ struct RandomizedSpriteGroup : SpriteGroup {
 	std::vector<const SpriteGroup *> groups{}; ///< Take the group with appropriate index:
 
 protected:
-	const SpriteGroup *Resolve(ResolverObject &object) const override;
+	ResolverResult Resolve(ResolverObject &object) const override;
 };
 
 
@@ -211,10 +218,12 @@ struct CallbackResultSpriteGroup : SpriteGroup {
 	 * Creates a spritegroup representing a callback result
 	 * @param value The value that was used to represent this callback result
 	 */
-	explicit CallbackResultSpriteGroup(uint16_t value) : SpriteGroup(SGT_CALLBACK), result(value) {}
+	explicit CallbackResultSpriteGroup(CallbackResult value) : SpriteGroup(SGT_CALLBACK), result(value) {}
 
-	uint16_t result = 0;
+	CallbackResult result = 0;
-	uint16_t GetCallbackResult() const override { return this->result; }
+
+protected:
+	ResolverResult Resolve(ResolverObject &object) const override;
 };
 
 
@@ -311,7 +320,7 @@ struct ResolverObject {
 
 	virtual ~ResolverObject() = default;
 
-	const SpriteGroup *DoResolve()
+	ResolverResult DoResolve()
 	{
 		return SpriteGroup::Resolve(this->root_spritegroup, *this);
 	}
@@ -342,8 +351,9 @@ public:
 	inline const TSpriteGroup *Resolve()
 	{
 		auto result = this->DoResolve();
-		if (result == nullptr || result->type != TSpriteGroup::TYPE) return nullptr;
+		const auto *group = std::get_if<const SpriteGroup *>(&result);
-		return static_cast<const TSpriteGroup *>(result);
+		if (group == nullptr || *group == nullptr || (*group)->type != TSpriteGroup::TYPE) return nullptr;
+		return static_cast<const TSpriteGroup *>(*group);
 	}
 
 	/**
@@ -364,13 +374,14 @@ public:
 	 * Resolve callback.
 	 * @return Callback result.
 	 */
-	inline uint16_t ResolveCallback()
+	inline CallbackResult ResolveCallback()
 	{
-		const SpriteGroup *result = this->DoResolve();
+		auto result = this->DoResolve();
-		return result != nullptr ? result->GetCallbackResult() : CALLBACK_FAILED;
+		const auto *value = std::get_if<CallbackResult>(&result);
+		return value != nullptr ? *value : CALLBACK_FAILED;
 	}
 
-	virtual const SpriteGroup *ResolveReal(const RealSpriteGroup &group) const;
+	virtual ResolverResult ResolveReal(const RealSpriteGroup &group) const;
 
 	virtual ScopeResolver *GetScope(VarSpriteGroupScope scope = VSG_SCOPE_SELF, uint8_t relative = 0);
 

src/newgrf_station.cpp

@@ -519,11 +519,11 @@ uint32_t Waypoint::GetNewGRFVariable(const ResolverObject &, uint8_t variable, [
 	return UINT_MAX;
 }
 
-/* virtual */ const SpriteGroup *StationResolverObject::ResolveReal(const RealSpriteGroup &group) const
+/* virtual */ ResolverResult StationResolverObject::ResolveReal(const RealSpriteGroup &group) const
 {
 	if (this->station_scope.st == nullptr || !Station::IsExpected(this->station_scope.st)) {
 		if (!group.loading.empty()) return group.loading[0];
-		return nullptr;
+		return std::monostate{};
 	}
 
 	uint cargo = 0;
@@ -566,7 +566,7 @@ uint32_t Waypoint::GetNewGRFVariable(const ResolverObject &, uint8_t variable, [
 	}
 
 	if (!group.loading.empty()) return group.loading[0];
-	return nullptr;
+	return std::monostate{};
 }
 
 GrfSpecFeature StationResolverObject::GetFeature() const

src/newgrf_station.h

@@ -75,7 +75,7 @@ struct StationResolverObject : public SpecializedResolverObject<StationRandomTri
 		}
 	}
 
-	const SpriteGroup *ResolveReal(const RealSpriteGroup &group) const override;
+	ResolverResult ResolveReal(const RealSpriteGroup &group) const override;
 
 	GrfSpecFeature GetFeature() const override;
 	uint32_t GetDebugID() const override;