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(C++ using G++) Create a DLL

Before being able to call a DLL, one has to create a DLL first.

To create a DLL using G++, do the following steps:

Create a DLL entry point with a WinMain

Create a unit with the functions you want to put in a DLL

Build the DLL

UnitEntryPoint.cpp

//---------------------------------------------------------------------------

#include <windows.h>

//---------------------------------------------------------------------------

int WINAPI DllEntryPoint(HINSTANCE hinst, unsigned long reason, void* lpReserved)

{

return 1;

}

//---------------------------------------------------------------------------

int WINAPI WinMain(

HINSTANCE hInstance,

HINSTANCE hPrevInstance,

LPSTR lpCmdLine,

int nCmdShow)

{

return 0;

}

//---------------------------------------------------------------------------

* View this code in plain text.

UnitFunctions.h

//---------------------------------------------------------------------------

#ifndef UnitFunctionsH

#define UnitFunctionsH

//---------------------------------------------------------------------------

#ifdef __cplusplus

extern "C"

{

#endif

__declspec (dllexport) const int GetAnswerOfLife();

#ifdef __cplusplus

}

#endif

//---------------------------------------------------------------------------

#endif

* View this code in plain text

The function put in the DLL is called GetAnswerOfLife and will return the value of 42. Note the #ifdef's before and after the function. These are obligatory!

Now the function GetAnswerOfLife must be defined in UnitFunctions.cpp. Upon viewing it, the code looks like below

UnitFunctions.cpp

//---------------------------------------------------------------------------

#include "UnitFunctions.h"

//---------------------------------------------------------------------------

const int GetAnswerOfLife()

{

return 42;

}

//---------------------------------------------------------------------------

* View this code in plain text.

Building the DLL

Use the following G++ commands:

g++ -c UnitFunctions.cpp

g++ -c UnitEntryPoint.cpp

g++ -o Functions.dll UnitEntryPoint.o UnitFunctions.o

This should yield your first DLL!

Perhaps you now want to go to the calling a DLL page.

Or download all source code of this page at once.

Go back to Richel Bilderbeek's C++ page.

Go back to Richel Bilderbeek's homepage.