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VC++: Weird problem with DLLs

Posted on 1998-02-16
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Last Modified: 2010-04-10
I am trying to figure out how to use other peoples' DLLs in Visual C++, but for some reason I can't seem to load the DLL into memory. I tried the following:

Created a new MFC application (.exe) and added the following code fragment anywhere (for example in CTestView::OnDraw):

HINSTANCE hlib = AfxLoadLibrary("commdlg.dll");
DWORD error = GetLastError();

When I step through this code I see that hlib obtains the value 0 (load failure) and error is equal to 31, which is the error code for General Failure Error. What in the world does a general failure error have to do with loading a DLL? The same result occurs regardless of the DLL I am using (I used commdlg.dll because I know it's a DLL that works). I know that error 31 is originating from AfxLoadLibrary because when I use GetLastError before the call to AfxLoadLibrary I get an error code 0 (success).

What is going on here? I doubt the General Failure error is really what's going on because everything in my OS is working properly (including things that other programs load from the commdlg.dll library). How can I solve this problem?
(Please don't tell me that I can use MFC functions that call commdlg.dll. I've already tried it, and it works. That library name is only an example. The same result happens no matter what DLL I try to load, this is just so that you can try the above code fragment on your computer if you want).

Thanks in advance!

-- Slarti
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Question by:Slarti
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galkin earned 100 total points
ID: 1182344
I guess you mistake is that you trying to load commdlg.dll which is 16 bit DLL into 32 address space of your EXE. try to load 32 bit version of this DLL comdlg32.dll
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by:Slarti
ID: 1182345
That is probably the problem, then. But I would still like to be able to load 16-bit DLLs into memory. (The problem is that I am trying to interface with a device driver written for Windows 3.1). How can I load a 16-bit DLL?
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Expert Comment

by:donleyp
ID: 1182346
You cannot load a Win16 DLL into a Win32 program's address space. Win32s provided a way for you to do this, but I don't know if it's even supported anymore. Furthermore, Trying to interface to a Win16 device driver in a Win32 environment is extremely dangerous if not impossible. How can you interface to it if the OS won't even load it? Even if you wrote a Win16 program and loaded the driver file directly, Windows would prevent you from accessing the device without going through bona-fide drivers.
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