Wrap c++ static library (.lib) functions into a DLL - dllexport

Question

I have a static library file (.lib) called SampleArithmetic.lib and the header file for it SampleArithmetic.h. Now using these files, I want to generate a DLL files for the functions present in the SampleArithmetic.lib.

What I did:

• Created a new project in VS2022 of type Class Library

• Configured include folder path (to access SampleArithmetic.h)

• Configured lib path and the lib required (i.e. SampleArithmetic.lib)

• and finally, added the code below in a .cpp file called SampleArithmeticDLLGenerator.cpp

    #include "SampleArithmetic.h"
    #include "pch.h"
  
    extern "C" {
        __declspec(dllexport) int add(int a, int b)
        {
            SampleArithmetic obj;
            return obj.Add(a, b);
        }
  
        __declspec(dllexport) int subtract(int a, int b)
        {
            SampleArithmetic obj;
            return obj.Subtract(a, b);
        }
  
        __declspec(dllexport) int multiply(int a, int b)
        {
            SampleArithmetic obj;
            return obj.Multiply(a, b);
        }
    }
  

PROBLEM:

I am getting the following errors:

Severity Code Description Project File Line Suppression State Error C2065 'SampleArithmetic': undeclared identifier CPlusPlusDLLWrapper C:\Users\Downloads\TestProject\TestCppLibIntegrationInCSharp\CPlusPlusDLLWrapper\SampleArithmeticDLLGenerator.cpp 7

Severity Code Description Project File Line Suppression State Error C2065 'obj': undeclared identifier CPlusPlusDLLWrapper C:\Users\Downloads\TestProject\TestCppLibIntegrationInCSharp\CPlusPlusDLLWrapper\SampleArithmeticDLLGenerator.cpp 7