Excel function adding two numbers returns zero when calling a function from a c++.dll

Question

I am using Excel Version 2206 Build 16.0.15330.20260 (64-bit) and Visual Studio Community 2022. I am trying to figure out how to call functions from a.dll in VBA, and I built my VBA module and.dll from this tutorial here: https://scriptreference.com/interfacing-ac-dll-with-excel-2016-using-visual-studio-2019/ .

The function shown in the tutorial where one reference is passed through the function works, however, when I added my own function to add two numbers by passing in two references, the VBA wrapper function I made in Excel only returns zero. I tried to find more resources online, such as.dll functions using multiple parameters in Excel VBA, but was not able to find any.

My source.cpp file looks like this:

#include "pch.h"
#include "SquareLib.h"

double WINAPI get_square(double* x) //function copied from tutorial that works
{
    return *x * *x;
}

double WINAPI add_nums(double* x, double* y) //my function
{
    return *x + *y;
}

The header file:

#pragma once

#ifdef SQUARELIB_EXPORTS
#define SQUARELIB_API __declspec(dllexport)
#else
#define SQUARELIB_API __declspec(dllimport)
#endif


extern "C" SQUARELIB_API double get_square(double* x);
extern "C" SQUARELIB_API double add_nums(double* x, double* y);

I compiled and built my solution in VS as a x64 bit.dll.

The code in VBA/Excel:

Declare PtrSafe Function get_square_cpp _
        Lib "C:\Users\artil\source\repos\SquareLib\x64\Debug\SquareLib.dll" Alias "get_square" _
        (ByRef my_var As Double) As Double

Declare PtrSafe Function add_nums_cpp _
        Lib "C:\Users\artil\source\repos\SquareLib\x64\Debug\SquareLib.dll" Alias "add_nums" _
        (ByRef x As Double, ByRef y As Double) As Double

Function get_square(x As Double) 'square wrapper function
    get_square = get_square_cpp(x)
End Function

Function add_num(x As Double, y As Double) 'add_num wrapper function
    add_nums = add_nums_cpp(x, y)
End Function

When I call the wrapper function add_num() as a formula in Excel, it returns 0, instead of adding the two numbers. I've looked online to see whether or not I'm using pointers incorrectly, but I didn't find anything saying my c++ function shouldn't work. I'm really new to c++, so I might've missed something.

Thanks in advance.

Answer 1

There was a simple spelling error for the name of the wrapper function in VBA/Excel. add_nums() was missing an s at the end. Thanks to @jasonliam for spotting it.