Attaching a process and creating a new thread using the Windows DLL




// Reuse the previous testdll project. Source file name: testdll.cpp, using moredll.dll

// that uses Dllmain(). You may create a new empty Win32 console mode application but make sure this program can find the DLL lor

// Using Run-Time Dynamic Linking which is a simple program that uses LoadLibrary() and GetProcAddress() to access Dllmain() of moredll.dll.

// No function to be exported/imported, just for testing

#include <stdio.h>

#include <windows.h>


typedef void (*MYPROC)(LPTSTR);


int main(void)




BOOL fFreeResult, fRunTimeLinkSuccess = FALSE;


// Get a handle to our DLL module, moredll.dll...this module has been copied to C:\WINDOWS\System32 directory (for Win Xp Pro SP2, change appropriately)

hinstLib = LoadLibrary(L"moredll");


// If the handle is valid, try to get the function address.

if (hinstLib != NULL)


printf("The DLL handle is valid...\n");

// The "Anonymfunction" function is fictitious. So expect the function address is not valid or error code 127

ProcAdd = (MYPROC) GetProcAddress(hinstLib, "Anonymfunction");


// If the function address is valid, call the function.

if (ProcAdd != NULL)


printf("The function address is valid...\n\n");

fRunTimeLinkSuccess = TRUE;

// Ready to execute DllMain()...



printf("The function address is not valid, error: %d.\n", GetLastError());



printf("\nThe DLL handle is NOT valid, error: %d\n", GetLastError());


// Free up the DLL module.

fFreeResult = FreeLibrary(hinstLib);

if (fFreeResult != 0)

printf("FreeLibrary() is OK.\n");


printf("FreeLibrary() is not OK.\n");

return 0;



Output example:


Loading the DLL...

The attached process creating a new thread...

The DLL handle is valid...

The function address is not valid, error: 127.

DLL unloading...

FreeLibrary() is OK.

Press any key to continue . . .


Compiler: Visual C++ Express Edition 2005

Compiled on Platform: Windows Xp Pro SP2

Target platform: none, just for learning and fun

Header file: Standard and Windows

Additional library: Windows Platform SDK

Additional project setting: Set project to be compiled as C.

Project->your_project_name Properties->Configuration Properties->C/C++->Advanced->Compiled As: Compiled as C Code (/TC)

Other info: non-CLR or unmanaged. Need to add Advapi32.lib (Advapi32.dll) to the project. Click the Project menu->Select the your_project_name Properties... sub menu->Expand the Configuration Properties folder on the left pane->Expand the Linker subfolder->Select the Input subfolder->Select the Additional Dependencies field on the right pane->Click the ... at the end of the field->Type in 'Advapi32.lib' in the empty pane->Click the OK button->Click the OK button second time to close the project Properties dialog.

To do: Attaching a process and creating a new thread using DLL

To show: The Windows DLL programming using Win32




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