Harden Luau userdata construction and runtime error handling

Guard userdata destruction when construction fails, validate package searchers, and reject saved persistence callbacks. Add regression coverage and clean up includes, local style and public build-directory examples.

Author: NixAJ

.github/workflows/luau-runtime.yml

@@ -15,8 +15,8 @@ jobs:
     steps:
       - uses: actions/checkout@v6
       - name: Configure
-        run: cmake -S tests -B TestBuilds/Runtime-luau -DLUA_VERSION=luau -DLUA_STATIC=ON -DCMAKE_BUILD_TYPE=Debug
+        run: cmake -S tests -B build/luau-runtime -DLUA_VERSION=luau -DLUA_STATIC=ON -DCMAKE_BUILD_TYPE=Debug
       - name: Build
-        run: cmake --build TestBuilds/Runtime-luau --config Debug --target eluna-runtime-tests --parallel 4
+        run: cmake --build build/luau-runtime --config Debug --target eluna-runtime-tests --parallel 4
       - name: Test
-        run: ctest --test-dir TestBuilds/Runtime-luau -C Debug --output-on-failure
+        run: ctest --test-dir build/luau-runtime -C Debug --output-on-failure

ElunaCompat.cpp

@@ -90,26 +90,23 @@ void luaL_setmetatable(lua_State* L, const char* tname) {
 #endif
 
 #if defined ELUNA_LUAU
-int luaL_ref(lua_State* L, int table)
-{
+int luaL_ref(lua_State* L, int table) {
     if (table != LUA_REGISTRYINDEX)
         return luaL_error(L, "Eluna's Luau references require the registry");
     int ref = lua_ref(L, -1);
     lua_pop(L, 1); // lua_ref itself does not consume the referenced value.
     return ref;
 }
 
-void luaL_unref(lua_State* L, int table, int ref)
-{
+void luaL_unref(lua_State* L, int table, int ref) {
     if (table != LUA_REGISTRYINDEX)
         luaL_error(L, "Eluna's Luau references require the registry");
     lua_unref(L, ref);
 }
 #endif
 
 #if defined ELUNA_LUAU || (LUA_VERSION_NUM == 501 && !defined LUAJIT_VERSION)
-void luaL_setfuncs(lua_State* L, const luaL_Reg* functions, int upvalues)
-{
+void luaL_setfuncs(lua_State* L, const luaL_Reg* functions, int upvalues) {
     luaL_checkstack(L, upvalues + 1, "too many upvalues");
     for (; functions->name; ++functions)
     {

ElunaCompat.h

@@ -11,6 +11,8 @@
 // Luau uses C++ linkage and exceptions. Do not wrap these headers in extern C.
 #include "lua.h"
 #include "lualib.h"
+#include <new>
+#include <utility>
 #else
 extern "C"
 {
@@ -41,6 +43,26 @@ extern "C"
 
     int luaL_ref(lua_State* L, int table);
     void luaL_unref(lua_State* L, int table, int ref);
+
+namespace ElunaLua
+{
+    template<typename T, typename... Args>
+    T* NewUserdata(lua_State* L, Args&&... args)
+    {
+        // Keep the object at offset zero for existing userdata casts. The
+        // trailing byte arms the destructor only after construction succeeds.
+        void* memory = lua_newuserdatadtor(L, sizeof(T) + 1, [](void* data)
+        {
+            if (static_cast<unsigned char*>(data)[sizeof(T)])
+                static_cast<T*>(data)->~T();
+        });
+        unsigned char& constructed = static_cast<unsigned char*>(memory)[sizeof(T)];
+        constructed = 0;
+        T* object = new (memory) T(std::forward<Args>(args)...);
+        constructed = 1;
+        return object;
+    }
+}
 #endif
 
 #if defined ELUNA_LUAU || LUA_VERSION_NUM == 501

ElunaLoader.cpp

@@ -11,6 +11,7 @@
 #include "ElunaUtility.h"
 #include "ElunaLuaRuntime.h"
 #include <fstream>
+#include <iterator>
 #include <sstream>
 #include <thread>
 #include <charconv>
@@ -33,8 +34,6 @@ namespace fs = std::filesystem;
 #include "Maps/MapManager.h"
 #endif
 
-#include "ElunaCompat.h"
-
 #if defined ELUNA_TRINITY
 void ElunaUpdateListener::handleFileAction(efsw::WatchID /*watchid*/, std::string const& dir, std::string const& filename, efsw::Action /*action*/, std::string /*oldFilename*/)
 {

ElunaLuaRuntime.cpp

@@ -88,6 +88,8 @@ namespace
         lua_pop(L, 1);
 
         lua_getfield(L, lua_upvalueindex(1), "searchers"); // 3: loaders
+        if (!lua_istable(L, 3))
+            return luaL_error(L, "package.searchers must be a table");
         std::string errors;
         for (int i = 1; ; ++i)
         {

ElunaTemplate.h

@@ -383,8 +383,7 @@ class ElunaTemplate
 
         // Create new userdata
 #if defined ELUNA_LUAU
-        ElunaObjectType* elunaObject = static_cast<ElunaObjectType*>(lua_newuserdatadtor(L, sizeof(ElunaObjectType),
-            [](void* memory) { static_cast<ElunaObjectType*>(memory)->~ElunaObjectType(); }));
+        ElunaObjectType* elunaObject = ElunaLua::NewUserdata<ElunaObjectType>(L, E, const_cast<T*>(obj), tname);
 #else
         ElunaObjectType* elunaObject = static_cast<ElunaObjectType*>(lua_newuserdata(L, sizeof(ElunaObjectType)));
 #endif
@@ -394,7 +393,9 @@ class ElunaTemplate
             lua_pushnil(L);
             return 1;
         }
+#if !defined ELUNA_LUAU
         new (elunaObject) ElunaObjectType(E, const_cast<T*>(obj), tname);
+#endif
 
         // Set metatable for it
         lua_pushstring(L, tname);

LuaValue.cpp

@@ -31,8 +31,6 @@
 #include "LuaValue.h"
 #include <stdio.h> // snprintf
 
-#include "ElunaCompat.h"
-
 LuaVal* LuaVal::GetLuaVal(lua_State* L, int index) {
     return static_cast<LuaVal*>(luaL_testudata(L, index, LUAVAL_MT_NAME));
 }
@@ -43,12 +41,11 @@ LuaVal* LuaVal::GetCheckLuaVal(lua_State* L, int index) {
 
 int LuaVal::PushLuaVal(lua_State* L, LuaVal const& lv) {
 #if defined ELUNA_LUAU
-    LuaVal* ud = static_cast<LuaVal*>(lua_newuserdatadtor(L, sizeof(LuaVal),
-        [](void* memory) { static_cast<LuaVal*>(memory)->~LuaVal(); }));
+    ElunaLua::NewUserdata<LuaVal>(L, lv.reference());
 #else
     LuaVal* ud = static_cast<LuaVal*>(lua_newuserdata(L, sizeof(LuaVal)));
-#endif
     new (ud) LuaVal(lv.reference());
+#endif
     luaL_setmetatable(L, LUAVAL_MT_NAME);
     return 1;
 }

docs/LUAU.md

@@ -10,9 +10,9 @@ Other emulator integrations have not been validated with Luau.
 From a workspace containing `Eluna/` and `ElunaTrinityWotlk/`:
 
 ```powershell
-cmake -S ElunaTrinityWotlk -B TestBuilds/Trinity-Luau -DELUNA=ON -DLUA_VERSION=luau -DLUA_STATIC=ON -DBUILD_TESTING=ON -DTOOLS=OFF
-cmake --build TestBuilds/Trinity-Luau --config Debug --target worldserver tests eluna-runtime-tests --parallel 6
-ctest --test-dir TestBuilds/Trinity-Luau -C Debug --output-on-failure
+cmake -S ElunaTrinityWotlk -B build/trinity-luau -DELUNA=ON -DLUA_VERSION=luau -DLUA_STATIC=ON -DBUILD_TESTING=ON -DTOOLS=OFF
+cmake --build build/trinity-luau --config Debug --target worldserver tests eluna-runtime-tests --parallel 6
+ctest --test-dir build/trinity-luau -C Debug --output-on-failure
 ```
 
 Use the generator and Boost, MySQL and OpenSSL paths required by your existing
@@ -24,9 +24,9 @@ The standalone runtime tests require only CMake, a C++ compiler and internet acc
 for the pinned Luau source archive:
 
 ```powershell
-cmake -S Eluna/tests -B TestBuilds/Runtime-luau -DLUA_VERSION=luau -DLUA_STATIC=ON
-cmake --build TestBuilds/Runtime-luau --config Debug --target eluna-runtime-tests
-ctest --test-dir TestBuilds/Runtime-luau -C Debug --output-on-failure
+cmake -S Eluna/tests -B build/luau-runtime -DLUA_VERSION=luau -DLUA_STATIC=ON
+cmake --build build/luau-runtime --config Debug --target eluna-runtime-tests
+ctest --test-dir build/luau-runtime -C Debug --output-on-failure
 ```
 
 For legacy runtime regression tests, use a separate build directory, select

lmarshal.cpp

@@ -429,6 +429,9 @@ static void mar_decode_value(lua_State *L, const char *buf, size_t len, const ch
             mar_incr_ptr(l);
         }
         else if (tag == MAR_TUSR) {
+#if defined ELUNA_LUAU
+            luaL_error(L, "Luau cannot load saved __persist callbacks; migrate instance saves to plain data before switching runtimes");
+#else
             mar_next_len(l, uint32_t);
             mar_check_len(l)
             lua_newtable(L);
@@ -439,6 +442,7 @@ static void mar_decode_value(lua_State *L, const char *buf, size_t len, const ch
             lua_pushvalue(L, -1);
             lua_rawseti(L, SEEN_IDX, (*idx)++);
             mar_incr_ptr(l);
+#endif
         }
         else {
             luaL_error(L, "bad encoded data");

tests/CMakeLists.txt

@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.18)
 
 # Also runnable without building the emulator or configuring its databases:
-# cmake -S Eluna/tests -B TestBuilds/runtime -DELUNA_LUALIB_DIR=<core>/dep/lualib
+# cmake -S Eluna/tests -B build/runtime -DELUNA_LUALIB_DIR=<core>/dep/lualib
 #       -DLUA_VERSION=luau -DLUA_STATIC=ON
 if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   project(ElunaRuntimeTests LANGUAGES C CXX)