Parse VC Create DLL, export global variables, functions and classes of in-depth analysis _c language

I. Creating a DLL
1. In VC, a new Win32 empty project mathlib;
2. Add precompiled Header file stdafx.h, define import export control symbols:

Copy Code code as follows:

StdAfx.h
#pragma once
#define Mathlib_export

3. Add the header file MathLib.h that contains the global variables, functions, and classes to export:

Copy Code code as follows:

MathLib.h
#pragma once

#ifdef Mathlib_export
#define MATHLIBAPI __declspec (dllexport)
#else
#define MATHLIBAPI __declspec (dllimport)
#endif

Macro
#define PI 3.14149

Global variable
extern Mathlibapi int globalvariable;

Function
MATHLIBAPI int Add (int a,int b);

Class
Class Mathlibapi Math
{
Public
int Multiply (int a,int b);
};

4. Add the implementation file for the exported element MathLib.cpp

Copy Code code as follows:

MathLib.cpp
#include "stdafx.h"
#include "MathLib.h"

int globalvariable = 100;

int Add (int a,int b)
{
return a+b;
}

int math::multiply (int a,int b)
{
return a*b;
}

Two, test the DLL you created
Test code:

Copy Code code as follows:

#include "stdafx.h"
#include <iostream>
using namespace Std;

#include ". /mathlib/mathlib.h "
#pragma comment (lib, "...). /debug/mathlib.lib ")

int _tmain (int argc, _tchar* argv[])
{
cout<< "Pi =" <<PI<<endl;

cout<< "globalvariable =" <<GlobalVariable<<endl;

int a = 20,b = 30;
cout<< "a=" <<a<< "," << "b=" <<b<<endl;
cout<< "a+b =" <<add (a,b) <<endl;

Math math;
cout<< "a*b =" <<math. Multiply (a,b) <<endl;

return 0;
}