DLL: "undefined reference to" - C (СИ)

/* Replace "dll.h" with the name of your header */
#include "dll.h"
#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
 
DLLIMPORT void HelloWorld ()
{
    MessageBox (0, "Hello World from DLL!\n", "Hi", MB_ICONINFORMATION);
}
 
DLLIMPORT void gg ()
{
          printf("privet");
          }
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;
}

#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_ */
 
DLLIMPORT void gg ();

#include"dll.h"
#include<conio.h>
main()
{
      gg();
      getch();
      }