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Calling DLL Function

Posted on 2002-05-10
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Last Modified: 2010-04-02
I want to have my application call a function in a DLL without linking to the DLL's header file. Here's how i defined the DLL function. How should I call it from my program?

__declspec(dllexport) void* CMyApp::DLLFUNC()
{
     m_ret = new COtherClass();
     return (void*)m_ret;
}
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Question by:qqqqqqqqq
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14 Comments
 

Author Comment

by:qqqqqqqqq
ID: 7002828
I have this much:
HMODULE hMod = LoadLibrary( "PathToMyDLL" );
Now that my DLL is loaded what should I do to call a specific function?
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Accepted Solution

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jhance earned 400 total points
ID: 7003016
First, determine the NAME of the EXPORT you want to call.  Use the Visual Studio tool DUMPBIN.EXE like:

DUMBIN /EXPORTS PathToMyDll.Dll

Find the exact name of your export function and then use the GetProcAddress() to get it's loaded address:

FARPROC myFunction;
myFunction = GetProcAddress(hMod, "NameYouFoundUsingDUMPBIN");
if(myFunction == NULL){
  // ERROR, function not found...
}
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Expert Comment

by:jhance
ID: 7003285
You have a number of open questions needing your attention:

Questions Asked 6
Last 10 Grades Given A B  
Question Grading Record 2 Answers Graded / 2 Answers Received


http://www.experts-exchange.com/jsp/qShow.jsp?ta=cplusprog&qid=20298614
http://www.experts-exchange.com/jsp/qShow.jsp?ta=cplusprog&qid=20294637
http://www.experts-exchange.com/jsp/qShow.jsp?ta=cplusprog&qid=20294243
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Expert Comment

by:jkr
ID: 7003425
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Author Comment

by:qqqqqqqqq
ID: 7003561
i know i have open questions but they are all active (all have a post within the last day)
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Author Comment

by:qqqqqqqqq
ID: 7003566
jhance: so how would I invoke the function after that?
jkr: your link doesn't load for me
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LVL 86

Expert Comment

by:jkr
ID: 7003594
just copied it from the brpwser: http://www.codeguru.com/win32/dyndllclass.shtml works...
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Author Comment

by:qqqqqqqqq
ID: 7003602
i have no access to the whole codeguru site, no clue why. Can you just post the code to call the function?
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LVL 32

Expert Comment

by:jhance
ID: 7003771
>>so how would I invoke the function after that?

myFunction();
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Author Comment

by:qqqqqqqqq
ID: 7003830
ok thanks. My problem is that when i try to run DUMPBIN.EXE i get errors about missing DLLs. I've tried re-installing VC++6. Is there a way to find the name of the function based on it's name in the source code? (It's not the same, because I tried the name of the function in the dll and the function wasn't invoked)
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Author Comment

by:qqqqqqqqq
ID: 7004141
nevermind about the dumpbin problem. I found the answer in a USENET group. I see that the function export name is: ?DLLFUNC@CMyApp@@QAEPAXXZ. I plan on using this code for multiple DLLs with the same function in them. It seems like the ?DLLFUNC@CMyApp@@ part will be the same but will the QAEPAXXZ part change? If so, is there a way to modify this to work with multiple DLLs?
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LVL 49

Expert Comment

by:DanRollins
ID: 7004756
If you don't haf a .DEF fiel for your DLL, add one like this:

; Merger.def : Declares the module parameters for the DLL.

LIBRARY      "ABC_Plugin"
DESCRIPTION  'Plugin Dynamic Link Library'

EXPORTS
    ; Explicit exports can go here
MyFirstExportedFn         @1
AnotherExportedFn         @2

-==-=-=-=-=-=-=-
That cleans up the 'decorations' on the exported fn names.

-- Dan
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Expert Comment

by:DanRollins
ID: 7004768
You can also view exported fn names using DEPENDS.EXE (it is a tool in the ...\Common\tools dir, available via the Start button.

-- Dan
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Author Comment

by:qqqqqqqqq
ID: 7004914
jhance: thank you very much
dan: thanks for the tip about cleaning up the name
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