Passing an interface from a Linux shared library

CMakeLists.txt (for consuming project)

cmake_minimum_required (VERSION 3.13)

project (ConsumingProject)

add_executable (ConsumingProject "ConsumingProject.cpp" "ConsumingProject.h")

if (UNIX)
	target_link_libraries(ConsumingProject "${CMAKE_DL_LIBS}") #Allows us to include dlfcn.h to link shared (dynamic) libraries
endif()

find_library(SHARED_LIB_LOCATION SharedLib PATHS ${CMAKE_BINARY_DIR}) #Assumes library's .so files have been copied into the same directory as this file
target_link_libraries(ConsumingProject "${SHARED_LIB_LOCATION}")

CMakeLists.txt (for SharedLib project)

cmake_minimum_required(VERSION 3.13) #3.13 was what I had on my WSL install.

project(SharedLib VERSION 0)
add_library(SharedLib SHARED "")
set_target_properties(SharedLib PROPERTIES VERSION ${PROJECT_VERSION})
set_target_properties(SharedLib PROPERTIES SOVERSION 1) #API Version

target_sources(SharedLib
    PUBLIC
        SharedLib.h
        SharedLib.cpp
        InterfaceTypes.h
		)

ConsumingProject.cpp

#include "ConsumingProject.h"
#include "InterfaceTypes.h"
#include <dlfcn.h>
#include <iostream>

int main()
{
	void* handle = dlopen("libSharedLib.so", RTLD_NOW);
	if (!handle)
	{
		std::cout << dlerror() << std::endl;
	}

	MyInterface theInterface;

	theInterface.GetCustomReturnType = (MyCustomReturnType(*)(MyCustomParameterType))dlsym(handle, "GetCustomReturnType");

	MyCustomParameterType param = 1;
	MyCustomReturnType returnStruct = theInterface.GetCustomReturnType(param);
  
  	char* error = dlerror();
	if (nullptr != error)
	{
		std::cout << error << std::endl;
	}
  	else
  	{
		std::cout << "Return value: " << returnStruct.Result << std::endl;
  	}
  
	dlclose(handle);
	return 0;
}

InterfaceTypes.h

#pragma once

extern "C"
{
	typedef long MyCustomParameterType;

	typedef struct MyCustomReturnType
	{
		long Result;
	} MyCustomReturnType;

	typedef struct MyInterface
	{
		MyCustomReturnType (*GetCustomReturnType)(MyCustomParameterType);
	} MyInterface;
}

SharedLib.cpp

#include "SharedLib.h"
#include <iostream>

MyCustomReturnType GetCustomReturnType(MyCustomParameterType param)
{
    std::cout << "Param value: " << param << std::endl;

    MyCustomReturnType returnStruct;
    returnStruct.Result = 123;
    return returnStruct;
}

SharedLib.h

#pragma once

#include "InterfaceTypes.h"

extern "C"
{
	MyCustomReturnType GetCustomReturnType(MyCustomParameterType param);
}