LuaStack returning null values

[miceiken]

So, I've started to code a bit on an injection project. Using EasyHook I've successfully managed to inject my DLL and hook EndScene. I've also managed to get DoString (FrameScript__Execute) to work correctly, however, when it comes to reading LUA return values, it seems that when I am trying to read from the LuaStack using GetTop and ToLString it just returns null. Here's some related code:

public static List<string> GetReturnVal(string lua, string file)
{
    Log.Output("Lua.GetReturnVal({0})", lua);
    lock (Dostringlock)
    {
        IntPtr pState = GetLuaStateHandler();
        int originalTop = GetTopHandler(pState);

        try
        {
            RunStatus status = LuaLoadHandler(pState, lua, lua.Length, file);

            if (status != RunStatus.Ok)
            {
                Log.Output("LuaLoad Failed!");
                ShowLuaStack(pState);
                return null;
            }

            status = LuaPCallHandler(pState, 0, -1, -2);
            if (status == RunStatus.Ok)
            {
                var stack = new List<string>();

                int argCount = GetTopHandler(pState);
                if (argCount > originalTop)
                {
                    for (int i = originalTop + 1; i <= argCount; i++)
                    {
                        stack.Add(LuaTolStringHandler(pState, i, 0));
                    }
                }

                Log.Output("GetReturnVal succeeded");
                ShowLuaStack(pState);
                return stack;
            }

            Log.Output("LuaPCall failed: {0}", status);
            ShowLuaStack(pState);
            return null;
        }
        catch (Exception e)
        {
            Log.Output("Exception GetReturnValue: {0}", e.ToString());
            return null;
        }
        finally 
        {
            LuaSetTopHandler(pState, originalTop);
        }
    }
}

[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
private delegate int LuaGetTop(IntPtr pLuaState);

[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
private delegate void LuaSetTop(IntPtr pState, int data);


[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
private delegate string LuaTolString(IntPtr pLuaState, int index, int lenght);

[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
private delegate IntPtr GetLuaState();

[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
private delegate RunStatus LuaPCall(IntPtr pState, int nargs, int nresults, int errfunc);

[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
private delegate RunStatus LuaLoad(IntPtr pState, string dataToLoad, int dataLength, string chunkName);

public enum LuaOffsets : uint
{
    GetLuaState = 0x004B1E50,
    GetTop = 0x00488A80,
    ToLString = 0x00488F90,
    DoString = 0x004B32B0,
    Load = 0x00974F00,
    PCall = 0x00489B00,
    SetTop = 0x00488AA0,
}

I will be very gratefull for any help!

[JuJuBoSc]

DoString don't put return value on the stack, you need to register your own callback and get result from here.

Look at BabBot source code as I remember they managed to use this way.

[miceiken]

I don't use DoString for this. I use LuaLoad and LuaPCall

[miceiken]

No suggestions?

[berserk85]

1) Is RunStatus.Ok == 0 ??
2) Are you sure that all return are String ? (if i can remember well LUA auto cast it but i'm not sure)
3)You should push Function name and function Parameter.
4) LuaPCallHandler(pState, 0, -1, -2) ... I think you should add more Lua function parameter ... LuaPCallHandler(pState, numOfFunctionParam, -1, 0)

A code snip from my project (there is QTlist but is simple linked list)

QList<QVariant> LuaAdaptor::ExecuteFunction(QString FunctionName,QList<QVariant> in )
{
	CINJ_INMAINLOOP
	QList<QVariant> ret;
	void *L;
	L = GetLuaState();

	int level = Lua_gettop(L);
	std::cerr << "level pre : " << level << std::endl;
	Lua_Getglobal(L, FunctionName.toLatin1().data());  /* get function */

	QVariant Element;
	foreach(Element , in)
	{
		switch (Element.type())
		{
			case 1:
				Lua_pushboolean(L,Element.toBool());
				break;

			case 2:
				Lua_pushinteger(L,Element.toInt());
				break;

			case 10:
				Lua_pushstring(L,Element.toString().toLatin1().data(),Element.toString().length());
				break;

			case 6:
				Lua_pushnumber(L,Element.toDouble());
				break;

			default:
				std::cerr << "Parsing Error" << std::endl;
		}
	}

	
	if (Lua_pcall(L, in.length(), LUA_MULTRET, 0) != 0)  /* do the call */
		std::cerr << "CinJ::LuaAdaptor Error running pfunction " << FunctionName.toLatin1().data() << " ( " << Lua_tostring(L, -1,0) << " )" << std::endl ;

	
	int num_of_result = Lua_gettop(L) - level;

	for(int i = Lua_gettop(L) ; i > level ; i--)
	{

		switch (Lua_type(L,i))
		{
			case LUA_TBOOLEAN:
				//ret.prepend()
				ret.prepend(QVariant(Lua_toboolean(L,i)));
				break;
			case LUA_TNUMBER:
				ret.prepend(QVariant(Lua_tonumber(L,i)));
				break;
			case LUA_TSTRING:
				ret.prepend(QVariant(Lua_tostring(L,i,0)));
				break;
			case LUA_TNIL:
				ret.prepend(QVariant("nil"));
				break;
			default:
				std::cerr << "CinJ::LuaAdaptor::FixMe Returned an unmanaged type" << Lua_type(L,i) << std::endl;
		}

	}
	Lua_settop(L, level);
	return ret;
}

[miceiken]

Thanks for showing me that the problem lies in what I pass on with LuaPCall, before I implemented the function name and functionparams thing, I wanted to check if it actually would return anything, so I tested:

// pState, nargs, nresults, errfunc 
// 1 argument in UnitName
status = LuaPCallHandler(pState, 1, -1, 0);

 13:23:06  Lua.GetReturnVal(UnitName("player");)
 13:23:06  LuaPCall failed: ErrRun