From 1b01a0636c874e423cac7d47055cbce7b10e9715 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Guilloux?= <glx22@users.noreply.github.com>
Date: Thu, 17 Jul 2025 13:30:33 +0200
Subject: [PATCH] Fix #14362, 4b677e8256: Don't crash old scripts doing silly
 instantiation (#14394)

---
 bin/ai/compat_14.nut           |  8 ++++++++
 bin/game/compat_14.nut         |  8 ++++++++
 src/script/script_instance.cpp | 12 ++++++++++++
 3 files changed, 28 insertions(+)

diff --git a/bin/ai/compat_14.nut b/bin/ai/compat_14.nut
index 012a8d070c..721278c24e 100644
--- a/bin/ai/compat_14.nut
+++ b/bin/ai/compat_14.nut
@@ -36,3 +36,11 @@ AITown.FoundTown <- function(tile, size, city, layout, name) { return AITown.Fou
 
 AIVehicle.SetNameCompat14 <- AIVehicle.SetName;
 AIVehicle.SetName <- function(id, name) { return AIVehicle.SetNameCompat14(id, AICompat14.Text(name)); }
+
+AIObject.constructorCompat14 <- AIObject.constructor;
+foreach(name, object in CompatScriptRootTable) {
+	if (type(object) != "class") continue;
+	if (!object.rawin("constructor")) continue;
+	if (object.constructor != AIObject.constructorCompat14) continue;
+	object.constructor <- function() : (name) { AILog.Error("'" + name + "' is not instantiable"); }
+}
diff --git a/bin/game/compat_14.nut b/bin/game/compat_14.nut
index 757e2496f4..652f6724ca 100644
--- a/bin/game/compat_14.nut
+++ b/bin/game/compat_14.nut
@@ -81,3 +81,11 @@ GSTown.FoundTown <- function(tile, size, city, layout, name) { return GSTown.Fou
 
 GSVehicle.SetNameCompat14 <- GSVehicle.SetName;
 GSVehicle.SetName <- function(id, name) { return GSVehicle.SetNameCompat14(id, GSCompat14.Text(name)); }
+
+GSObject.constructorCompat14 <- GSObject.constructor;
+foreach(name, object in CompatScriptRootTable) {
+	if (type(object) != "class") continue;
+	if (!object.rawin("constructor")) continue;
+	if (object.constructor != GSObject.constructorCompat14) continue;
+	object.constructor <- function() : (name) { GSLog.Error("'" + name + "' is not instantiable"); }
+}
diff --git a/src/script/script_instance.cpp b/src/script/script_instance.cpp
index 6d493e4438..e321d515b8 100644
--- a/src/script/script_instance.cpp
+++ b/src/script/script_instance.cpp
@@ -130,6 +130,13 @@ bool ScriptInstance::LoadCompatibilityScripts(Subdirectory dir, std::span<const
 
 	ScriptLog::Info(fmt::format("Downgrading API to be compatible with version {}", this->api_version));
 
+	HSQUIRRELVM vm = this->engine->GetVM();
+	sq_pushroottable(vm);
+	sq_pushstring(vm, "CompatScriptRootTable");
+	sq_pushroottable(vm);
+	sq_newslot(vm, -3, SQFalse);
+	sq_pop(vm, 1);
+
 	/* Downgrade the API till we are the same version as the script. The last
 	 * entry in the list is always the current version, so skip that one. */
 	for (auto it = std::rbegin(api_versions) + 1; it != std::rend(api_versions); ++it) {
@@ -138,6 +145,11 @@ bool ScriptInstance::LoadCompatibilityScripts(Subdirectory dir, std::span<const
 		if (*it == this->api_version) break;
 	}
 
+	sq_pushroottable(vm);
+	sq_pushstring(vm, "CompatScriptRootTable");
+	sq_deleteslot(vm, -2, SQFalse);
+	sq_pop(vm, 1);
+
 	return true;
 }