Calling function in dll 2

[titanandrews]

Hi,
I am having a bit of trouble with this one. All I want to do is call a function that is in a dll that I created. The dll gets loaded put I cannot make the function call. What am I missing??

//Here is my dll code

#include <iostream>


void __declspec(dllexport)__stdcall doIt()
{
	std::cout << &quot;doIt function called &quot; << std::endl;
}

//And here is my calling code in the executable

#include "afx.h"
#include <iostream>

using namespace std;

int main(int argc, char* argv[])
{
    HANDLE dllHandle;
	typedef void (__stdcall *MY_PROC)(void);
	MY_PROC doIt;
	dllHandle = LoadLibrary((LPCTSTR) &quot;MyDll.dll&quot;); 
	if (dllHandle == NULL)
	{
		cout << &quot;MyDll.dll failed to load...&quot; << endl;
		exit(0);
    }
    
	doIt = (MY_PROC)GetProcAddress((HINSTANCE)dllHandle, &quot;doIt&quot;); 	
	if (doIt == NULL)
	{
		cout << &quot;doIt failed...&quot; << endl;
	}
	else doIt();
   
    return(1);
}

many thanks,

Barry

 

[JOLESEN]

Is the function doIt() actually exported ?

You can check if it is using dumpbin /EXPORTS dllname.dll

Dumpbin is a console program included with VC.

/JOlesen

 

[sambasivamkannan]

When you call the the function you should call it like this:
(*doIt)();

because doIt is a pointer to a function.
-S.Kannan

 

[titanandrews]

This is the output I get using the dumpbin program:

Microsoft (R) COFF Binary File Dumper Version 6.00.8447
Copyright (C) Microsoft Corp 1992-1998. All rights reserved.


Dump of file H:\CSTUFF\MYDLL\CallMyDll\DEBUG\MyDll.dll

File Type: DLL

  Section contains the following exports for MyDll.dll

           0 characteristics
    3F25D48F time date stamp Mon Jul 28 21:57:35 2003
        0.00 version
           1 ordinal base
           1 number of functions
           1 number of names

    ordinal hint RVA      name

          1    0 0000108C ?doIt@@YGXXZ

  Summary

        8000 .data
        1000 .idata
        4000 .rdata
        3000 .reloc
       3C000 .text

Yes, I know doIt() is a pointer:

typedef void (__stdcall *MY_PROC)(void);

I check to see if it's NULL, and it always is. Just for kicks, I tried calling it like (*doIt)(); as S.Kannan suggested and it still doesn't work. Any ideas?



thanks,


Barry

 

[sambasivamkannan]

I tried the following code and it worked. All I did is to add a DEF file to the dll project.
***************************************************************
// DLL part

void __declspec(dllexport)__stdcall doIt()
{
AfxMessageBox("doIt"
}


************************************************************
//// Client part
{
HINSTANCE dllHandle;
typedef void (*MY_PROC)();
MY_PROC doXIt;
dllHandle = ::LoadLibrary("dll.dll"
if (dllHandle == NULL)
{
AfxMessageBox("Dll failed to load"
return;

}

doXIt = (MY_PROC)GetProcAddress(dllHandle, "doIt"
if (doXIt == NULL)
{
AfxMessageBox("Unable to get function address"
return;
}
else doXIt();

return;
}

I think when you dynamically load a library and call its function the dll project should contain a DEF file. It worked for me. It should work for you.

-S.Kannan

 

[sambasivamkannan]

To be more specific, the DEF file should contain an entry for the exported function