How to use KeraLua.Lua.NewUserData correctly

[maikgreubel]

Hello,

I do not know how to use the function KeraLua.Lua.NewUserData() correctly. I get a valid IntPtr object from it but do not know how to dereference it to a structure. The following code is a stripped-down snippet which causes a System.ExecutionEngineException at:

Fatal error. Internal CLR error. (0x80131506)
   at System.StubHelpers.InterfaceMarshaler.ConvertToManaged(IntPtr, IntPtr, IntPtr, Int32)
   at System.Runtime.InteropServices.Marshal.PtrToStructureHelper(IntPtr, System.Object, Boolean)
   at System.Runtime.InteropServices.Marshal.PtrToStructureHelper(IntPtr, System.Type)
   at System.Runtime.InteropServices.Marshal.PtrToStructure(IntPtr, System.Type)
   at NLuaExperiments.KeraLuaTest.Start()
   at NLuaExperiments.Program.Main(System.String[])

using NLua;
using System;
using System.Runtime.InteropServices;

namespace NLuaExperiments
{
    public struct UserData
    {
        public object Ref;
    }

    public class KeraLuaTest
    {
        private Lua lua;
        public KeraLuaTest(Lua lua)
        {
            this.lua = lua;
        }

        public void Start()
        {
            KeraLua.Lua state = lua.State;

            IntPtr p = state.NewUserData(Marshal.SizeOf(default(UserData)));
            UserData u = (UserData)Marshal.PtrToStructure(p, typeof(UserData));
        }
    }

    class Program
    {
        private static Lua lua = new();

        static void Main(string[] args)
        {
            new KeraLuaTest(lua).Start();
        }
    }
}

Does NewUserData() does not provide a valid memory pointer to use as structure?

[viniciusjarina]

To pass user data use ToObject and PushObject instead. https://github.com/NLua/KeraLua/blob/main/tests/Tests/Interop.cs#L50

[maikgreubel]

Indeed! Thank you very much! 😁