Thread: Need some help with Dlls

Well, the way i do it works when its only one dll.

I just made a test dll and made 2 copies of it to test this, is it not 'allowed'.

Edit: Also, here I am not trying to run any of the functions, if I try to run them (using GetProcAdress and assigning to variable of function definition) it works fine.

My main question here is why am I unable to load the dlls.

Ok, thanks for your reply, I did not know that

However, I created another dll with the functions

Code:

void __declspec (dllexport) getTestFunction2(char* placement, int size);
long int __declspec (dllexport) realTestTwo1243214();  //Yes, I'm too lazy to make up a more creative name :p

And it did not work with this either.

Edit: That is now the second dll I am loading, the first one is the one in original topic.
Edit2:

even across multiple copies of a program

What do you mean by this, I originally copied the dll, not the program.

Code:

#include <stdio.h>
#include <windows.h>

extern "C"{
    void __declspec (dllexport) getTestFunction2(char* placement, int size){
        snprintf(placement, size, "realTestTwo1243214");
        //snprintf(placement, size, "7zFunctionName");
        return;
    }
    
    
    long int __declspec (dllexport) realTestTwo1243214(){
         printf("Currently in the realTest function in the DLL! \x02\r\n");
         return 0;
    }
}

bool APIENTRY DllMain (HINSTANCE hInst, DWORD reason, LPVOID reserved)
{
    switch (reason)
    {
      case DLL_PROCESS_ATTACH:
        break;

      case DLL_PROCESS_DETACH:
        break;

      case DLL_THREAD_ATTACH:
        break;

      case DLL_THREAD_DETACH:
        break;
    }
    return TRUE;
}

That is the dll's code. The first dll is the same code, but with different function names


Edit: GetLastError returns 998 - Invalid access to memory location on 2nd dll.

Originally Posted by CommonTater

BECAUSE... windows does not load duplicate DLL files, even across multiple copies of a program...

Uh, what?

Windows has utterly no clue that the two DLLs are the "same." They aren't the same. They are separate files.

If you don't believe it, compile this:

Code:

#include <windows.h>
#include <stdio.h>

int main()
{
	HMODULE a = LoadLibrary("foo.dll");
	HMODULE b = LoadLibrary("bar.dll");

	printf("%p\n", a);
	printf("%p\n", b);
}

Then put two copies of the same DLL alongside the resulting EXE, naming them "foo.dll" and "bar.dll." No problem.

EDIT: Furthermore, yes, Windows will load DLLs multiple times between separate copies of the same program. If one copy of the program has allocated VM space at the DLLs preferred base address, the DLL will need to be rebased. In the other copy of the program the DLL was not rebased (or was rebased to yet a different location). It will share them if it CAN. If it can't, it's no disaster, it just loads it again.

Originally Posted by dumazz

Well, found a resource that might be of some help: PRB: LoadLibrary API Fails with 998 (ERROR_NOACCESS) Error
This seems to be the error that is happening.

You mean that's the error code you get when you call GetLastError()?

Can you post the contents of DllMain() in the DLL in question?