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Link Explicitly

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With explicit linking, applications must make a function call to explicitly load the DLL at run time. To explicitly link to a DLL, an application must:

  • Call LoadLibrary (or a similar function) to load the DLL and obtain a module handle.

  • Call GetProcAddress to obtain a function pointer to each exported function that the application wants to call. Because applications are calling the DLL’s functions through a pointer, the compiler does not generate external references, so there is no need to link with an import library.

  • Call FreeLibrary when done with the DLL.

For example:

typedef UINT (CALLBACK* LPFNDLLFUNC1)(DWORD,UINT);
.
.
.
HINSTANCE hDLL;               // Handle to DLL
LPFNDLLFUNC1 lpfnDllFunc1;    // Function pointer
DWORD dwParam1;
UINT  uParam2, uReturnVal;

hDLL = LoadLibrary("MyDLL");
if (hDLL != NULL)
{
   lpfnDllFunc1 = (LPFNDLLFUNC1)GetProcAddress(hDLL,
                                           "DLLFunc1");
   if (!lpfnDllFunc1)
   {
      // handle the error
      FreeLibrary(hDLL);      
      return SOME_ERROR_CODE;
   }
   else
   {
      // call the function
      uReturnVal = lpfnDllFunc1(dwParam1, uParam2);
   }
}

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