Using Run-Time Dynamic Linking

You can use the same DLL in both load-time and run-time dynamic linking. The following example uses the LoadLibrary function to get a handle to the Myputs DLL (see Creating a Simple Dynamic-Link Library). If LoadLibrary succeeds, the program uses the returned handle in the GetProcAddress function to get the address of the DLL's myPuts function. After calling the DLL function, the program calls the FreeLibrary function to unload the DLL.

Because the program uses run-time dynamic linking, it is not necessary to link the module with an import library for the DLL.

This example illustrates an important difference between run-time and load-time dynamic linking. If the DLL is not available, the application using load-time dynamic linking must simply terminate. The run-time dynamic linking example, however, can respond to the error.

// A simple program that uses LoadLibrary and 
// GetProcAddress to access myPuts from Myputs.dll. 
 
#include <windows.h> 
#include <stdio.h> 
 
typedef int (__cdecl *MYPROC)(LPCWSTR); 
 
int main( void ) 
{ 
    HINSTANCE hinstLib; 
    MYPROC ProcAdd; 
    BOOL fFreeResult, fRunTimeLinkSuccess = FALSE; 
 
    // Get a handle to the DLL module.
 
    hinstLib = LoadLibrary(TEXT("MyPuts.dll")); 
 
    // If the handle is valid, try to get the function address.
 
    if (hinstLib != NULL) 
    { 
        ProcAdd = (MYPROC) GetProcAddress(hinstLib, "myPuts"); 
 
        // If the function address is valid, call the function.
 
        if (NULL != ProcAdd) 
        {
            fRunTimeLinkSuccess = TRUE;
            (ProcAdd) (L"Message sent to the DLL function\n"); 
        }
        // Free the DLL module.
 
        fFreeResult = FreeLibrary(hinstLib); 
    } 

    // If unable to call the DLL function, use an alternative.
    if (! fRunTimeLinkSuccess) 
        printf("Message printed from executable\n"); 

    return 0;

}

Related topics

Run-Time Dynamic Linking