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

 

Before being able to call a DLL, one has to create a DLL using g++ 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

 

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//--------------------------------------------------------------------------- #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; } //---------------------------------------------------------------------------

 

 

 

 

 

UnitFunctions.h

 

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//--------------------------------------------------------------------------- #ifndef UnitFunctionsH #define UnitFunctionsH //--------------------------------------------------------------------------- #ifdef __cplusplus extern "C" { #endif __declspec (dllexport) const int GetAnswerOfLife(); #ifdef __cplusplus } #endif //--------------------------------------------------------------------------- #endif

 

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

 

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//--------------------------------------------------------------------------- #include "UnitFunctions.h" //--------------------------------------------------------------------------- const int GetAnswerOfLife() {   return 42; } //---------------------------------------------------------------------------

 

 

 

 

 

Building the DLL

 

Use the following g++ commands:

 

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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 using g++.

 

Or download all source code of this page at once.