Help with LoadLibrary
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Thread: Help with LoadLibrary

  1. #1
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    Help with LoadLibrary

    Hi gurus!
    I'm using VC++ 7.0 and I created a console project:
    Code:
    #include "stdafx.h"
    #include "windows.h"
    int _tmain(int argc, _TCHAR* argv[])
    {      HMODULE hMod=LoadLibrary("mylib.dll");         //error 
    
             return 0;
    }
    The error is: 'error C2065: '' : undeclared identifier'.
    I dunno why. Help me!

  2. #2
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    First make sure the project compiles okay with the call to LoadLibrary().

    What OS is it?

    Kuphryn

  3. #3
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    code seems ok...
    First try cutting HMODULE hMod=LoadLibrary("mylib.dll"); line into :

    HMODULE hMod;
    hMod=LoadLibrary("mylib.dll");

    And see if the problem comes from LoadLibrary or from hmodule like that.

  4. #4
    John E is offline Elite Member Power Poster
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    This is a long shot.... The line

    #include "stdafx.h"

    indicates that this is an MFC app. MFC apps aren't supposed to #include "windows.h" explicitly. I can't remember why though.
    "A problem well stated is a problem half solved. - Charles F. Kettering

  5. #5
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    This is a long shot.... The line

    #include "stdafx.h"

    indicates that this is an MFC app. MFC apps aren't supposed to #include "windows.h" explicitly. I can't remember why though.
    seems that these files contain some #ifdef ... #undef stuff that cause the problem.

  6. #6
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    stdafx.h is just the name of the precompiled header that is auto generated from the wizard. What it contains depends on teh project type you choose. LoadLibrary(...) is a pretty standard function that is #defined pretty early on in the includes.

    You don't #include windows because it is already #included when you include various <afxXXX> headers.


    Are you sure it's LoadLibrary(...) and not _TCHAR that it is complaining about?

    At anyrate...forward declare it,depending if your using unicode (which you should be doing if your NT->) or what not. And find out what is wrong with your headers, because something is mucked up.

    Code:
    WINBASEAPI
    HMODULE
    WINAPI
    LoadLibraryExA(
        IN LPCSTR lpLibFileName,
        IN HANDLE hFile,
        IN DWORD dwFlags
        );
    WINBASEAPI
    HMODULE
    WINAPI
    LoadLibraryExW(
        IN LPCWSTR lpLibFileName,
        IN HANDLE hFile,
        IN DWORD dwFlags
        );

  7. #7
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    Hi, thanks for your helping. I'm using WinXP Pro. I've tried what you suggested:
    Code:
    #include "stdafx.h"
    int _tmain(int argc, _TCHAR* argv[])
    {      HMODULE hMod;
            hMod=LoadLibrary("mylib.dll");          //error 
    
             return 0;
    }
    There're still errors. One is: error C2065: '' : undeclared identifier'. and one is error C2440: '=' : cannot convert from ''unknown-type'' to 'HMODULE'
    And here is all of my "stdafx.h":
    Code:
    #pragma once
    #define WIN32_LEAN_AND_MEAN
    #include <windows.h>
    #include <tchar.h>
    #include <iostream>
    Help me pliz!
    Last edited by tdc; April 25th, 2004 at 04:07 PM.

  8. #8
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    1) Return type should ne HINSTANCE, but HMODULE

    2) You do not seem to have the correct header [winbase.h]. As a temp test, put the following line in your file.
    HINSTANCE LoadLibrary(
    LPCTSTR lpLibFileName // address of filename of executable module
    );
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  9. #9
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    I changed HMODULE -> HINSTANCE, but the error is error C2440: '=' : cannot convert from ''unknown-type'' to 'HINSTANCE'

    Anyway, when I added a file into my project:
    Code:
    //LoadLib.cpp
    #include "stdafx.h"
    unsigned MyLoadLib()
    {	HMODULE h= LoadLibrary("mylib.dll");
    	return 1;
    }
    everything's OK! I dunno what's going on...
    Last edited by tdc; April 25th, 2004 at 04:13 PM.

  10. #10
    John E is offline Elite Member Power Poster
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    You've repeatedly told us about the undeclared identifier but you still haven't said which symbol is unidentified. What is the entire error that you're getting?

    Also, is this an MFC application or not? If so, why does it have a 'main(...)' function? If not, why are you including stdafx.h?

    At the moment, we can only guess at this problem because you're keeping too much information to yourself. You'll have to be a bit more forthcoming if you want to be helped. Sorry...
    "A problem well stated is a problem half solved. - Charles F. Kettering

  11. #11
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    Originally posted by John E

    Also, is this an MFC application or not? If so, why does it have a 'main(...)' function? If not, why are you including stdafx.h?
    stdafx.h is just the name of the wizard auto generated pre-compiler header, it has nothing to do with MFC.

  12. #12
    John E is offline Elite Member Power Poster
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    Originally posted by Mick
    stdafx.h is just the name of the wizard auto generated pre-compiler header, it has nothing to do with MFC.
    Are you sure about that Mick? I always thought that Afx is MFC's implementation of the standard Windows components?? Stdafx.h normally #includes the MFC core component headers, as well as MFC support for common controls etc.
    "A problem well stated is a problem half solved. - Charles F. Kettering

  13. #13
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    Originally posted by John E
    Afx is MFC's implementation of the standard Windows components isn't it?? Stdafx.h normally #includes the MFC core component headers, as well as MFC support for common controls etc.
    What gets placed in the stdafx depends on what type of project you create through the wizard...it is just a precompiled header file name.

  14. #14
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    The entry-point function (like main()) should perform only simple initialization or termination tasks. It must not call the LoadLibrary or LoadLibraryEx function (or a function that calls these functions), because this may create dependency loops in the DLL load order. This can result in a DLL being used before the system has executed its initialization code. Similarly, the entry-point function must not call the FreeLibrary function (or a function that calls FreeLibrary), because this can result in a DLL being used after the system has executed its termination code.

  15. #15
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    The fact that the resolution was 'I just added a file and it now works' leads me to believe the whole problem revolved around the pch files, in which the OP either.

    1. Including something before the precomplied headers, in this case #include <stdafx.h> such as:

    #include <windows.h>
    #include <stdafx.h>

    With no <windows.h> included in the <stdafx.h> though we are shown that, that is apparently not the case.

    Or

    The precompiled headers got into some fubar state.

    Mr. Tomaszek: I'm not sure where you brought the DLL comment into the issue, as we are not dealing with a DLL.

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