C語言DLL編寫及引用

開發環境是DEV C++,採用C語言編寫
創建一個DLL項目


#ifndef _DLL_H_
#define _DLL_H_

#if BUILDING_DLL
# define DLLIMPORT __declspec (dllexport)
#else /* Not BUILDING_DLL */
# define DLLIMPORT __declspec (dllimport)
#endif /* Not BUILDING_DLL */


DLLIMPORT void HelloWorld (void);


#endif /* _DLL_H_ */

C文件
dllmain.c
#include 
#include 

DLLIMPORT void HelloWorld ()
{
    MessageBox (0, "Hello World from DLL!\n", "Hi", MB_ICONINFORMATION);
}


BOOL APIENTRY DllMain (HINSTANCE hInst     /* Library instance handle. */ ,
                       DWORD reason        /* Reason this function is being called. */ ,
                       LPVOID reserved     /* Not used. */ )
{
    switch (reason)
    {
      case DLL_PROCESS_ATTACH:
        break;

      case DLL_PROCESS_DETACH:
        break;

      case DLL_THREAD_ATTACH:
        break;

      case DLL_THREAD_DETACH:
        break;
    }

    /* Returns TRUE on success, FALSE on failure */
    return TRUE;
}

還有要注意的在.def文件中指定輸出的函數，編譯生成了hello.dll文件

DLL調用部分
dllcall.c
#include 
#include 
#include 

HINSTANCE hDLL; //定義DLL
typedef void ( *func)(); //定義函數指標 
func hello;  //定義函數指標
int main()
{
 if (hDLL == NULL)
    hDLL=LoadLibrary("hello.dll");  //加載DLL
 hello = (func)GetProcAddress(hDLL,"HelloWorld"); //獲取函數指標
 hello();
 FreeLibrary(hDLL);  //釋放DLL
 return 0;
}