How to use shared dll with common header

Question

Hi

I have a header file which has a class having one pure virtual function.

This class is inherited and implement a virtual function. This implemented class ia to be there in a dll project. How to export this function as I am facing issue to write extern "c" __declspec(dllexport) due to virtual I believe.

How to use virtual function implementation from shared dll to a different project ? Is there any other way or Am i missing something ?

Answer 1

Thanks but I am getting into linker error. I tried below:

commonHeader_Exp.h has following:
#pragma once
class myType
{
public:
virtual ~myType() {}
virtual void display() = 0;
};

commonHeader_Imp.h has following:
#pragma once

class __declspec(dllimport) myType
{
public:
virtual ~myType() {}
virtual void display() = 0;
};

Project related to DLL is DLL_A.sln. DLL_A.sln has header.h and Source.cpp.
header.h has following:
#pragma once
#include "d:\SelfLearning\LinkingTrial\commonHeader_Exp.h"

class myTypeImpl : public myType
{
public:
void display();
};

Source.cpp has following:
#include "pch.h"
#include "Header.h"
#include <iostream>

extern "C" __declspec(dllexport) myTypeImpl * getObject()
{
return new myTypeImpl;
}

void myTypeImpl::display()
{
std::cout << "Display from myTypeImpl of DLL A\n";
}

DLL project compiles fine.

Project related to client is client.sln and it has client.cpp.

client.cpp has following:
#include <iostream>
#include "d:\SelfLearning\LinkingTrial\commonHeader_Imp.h"
#include "d:\SelfLearning\LinkingTrial\DLL_A\DLL_A\Header.h"

int main()
{
myTypeImpl* pMyImpl;
pMyImpl->display();

return 0;
}

It does not compile. If I exclude commonHeader_imp.h from client, it is ok then but how to write those import related class in client.cpp?

Also with exclusion of commonHeader_imp.h, it fails to recognize gettype if done as below:
myTypeImpl* pMyImpl = getObject();

Again thanks a lot for your help..!