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LoadLibrary() returning NULL

DOrmisher · 2009-01-08T15:03:06

I am having a problem loading a run time dll, which I am attempting to do like so: HMODULE hMod = LoadLibrary( L"DLL_Negative.dll" ); function = (IMGFUNC) GetProcAddress( hMod, "DLL_Negative" ); function( m_Image ); I add a breakpoint at the line after LoadLibrary() call, and add a watch to the hMod, but the LoadLibrary keeps returning NULL. The project is an MFC app, so I tested the same code in a simple win 32 console app with the same dll, which worked. I have tried including the full file path, which won't work, and I have even tried to load a dll from the windows system folder, which also returns NULL. I have placed the dll in all the file locations i can think of, all to no avail. The windows.h header is included. Is there something different that must be done when loading a dll in this way when in an MFC application? Thanks in advance

General and Gameplay Programming Programming

Started by DOrmisher January 08, 2009 06:47 AM

13 comments, last by Zlodo 15 years, 3 months ago

Evil Steve

2,021

January 08, 2009 08:19 AM

Quote:Original post by DOrmisher
When I created the dll I used a win32 dll project, will this make any difference? Do you need to create an MFC DLL project for it to load correctly in an MFC app?

Nope. There's no relevant difference.

Quote:Original post by dmail
That maybe so Steve but I would think the note in LoadLibrary docs over rides that
Quote:
http://msdn.microsoft.com/en-us/library/ms684175.aspx
When specifying a path, be sure to use backslashes (\), not forward slashes (/).

Ah, that's true. I'm not sure why that would be really, forward slashes have always worked for me...

DOrmisher

100

Author

January 08, 2009 08:27 AM

I just moved the LoadLibrary() call to InitInstance() in the main source file, and it seems to be working correctly. Any idea why it won't work in an event handler for a button in a dialog class?

She got a hat and all that hat says is asshole

DOrmisher

100

Author

January 08, 2009 08:31 AM

The problem seems to be sorted now. If I declare the HMODULE variable inside the if statement. It works. Any ideas why?

She got a hat and all that hat says is asshole

Evil Steve

2,021

January 08, 2009 08:47 AM

Quote:Original post by DOrmisher
The problem seems to be sorted now. If I declare the HMODULE variable inside the if statement. It works. Any ideas why?

If that's your actual code, then it looks to me like your compiler is broken :P I'm assuming you're not using VC6.0, because if you are, be prepared for all sorts of bugs like this.

The only reason I can think it'd fail is if you're changing the current working directory somewhere, and not using a full path properly.

Zlodo

655

January 08, 2009 03:03 PM

Try to run your program with process monitor (http://technet.microsoft.com/en-us/sysinternals/bb896645.aspx) to see what exactly happens when you try to load the dll.

For instance, you should be able to see whether it's because the file was simply not found (in which case you should be able to see the failed open file called by LoadLibrary) or because of some other problem.

LoadLibrary() returning NULL

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