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Strange DLL problem...

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Join Date: Sep 2008

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daggath

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Strange DLL problem...

Sep 6th, 2008

Hi, I recently was trying to learn how to write DLLs and was doing ok until I ran across this interesting problem. It seems that the function is not receiving the last argument.

Here is my code for the dll

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#include "stdafx.h"
 
BOOL APIENTRY DllMain( HANDLE hModule, DWORD  ul_reason_for_call, LPVOID lpReserved)
{
    return TRUE;
}
 
_declspec (dllexport) int _stdcall sum(int x , int y)
{
	return (x+y);
}
#include "stdafx.h"

BOOL APIENTRY DllMain( HANDLE hModule, DWORD  ul_reason_for_call, LPVOID lpReserved)
{
    return TRUE;
}

_declspec (dllexport) int _stdcall sum(int x , int y)
{
	return (x+y);
}

and here is my .def file

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LIBRARY example1
 
EXPORTS
 
sum	@1

I am using visual studio C++ 2005 to write the dll and am using VB to call it. When I call sum it returns the value of x.. if I tell the dll to return y I always get 0 ... I can't figure it why. When I added more arguments to the function I found that it was always the last variable that always is received as 0. What is happening? What am I doing wrong?

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Ancient Dragon Ancient Dragon is offline

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Re: Strange DLL problem...

Sep 6th, 2008

how did you declare it in your vb program? what you posted appears to be correct. But you don't need both the *.def file and use of _dllspec(__export) -- all you need is one of them.

Don't PM me with questions -- you might get a nasty PM in response. If you have a question then post it in one of the forums.

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dougy83

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Re: Strange DLL problem...

Sep 6th, 2008

The VB declare statement should be:

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declare function sum lib "example1.dll" (byval x as long, byval y as long) as long
declare function sum lib "example1.dll" (byval x as long, byval y as long) as long

where example1.dll is the name of your dll file.

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daggath

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Re: Strange DLL problem...

Sep 6th, 2008

•

Originally Posted by dougy83

The VB declare statement should be:
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VB Syntax (Toggle Plain Text)
declare function sum lib "example1.dll" (byval x as long, byval y as long) as long
declare function sum lib "example1.dll" (byval x as long, byval y as long) as long
where example1.dll is the name of your dll file.

yes that is what I basicly have...

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Public Class Form1
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
 
        Button1.Text = Str(sum(CInt(TextBox1.Text), CInt(TextBox2.Text)))
    End Sub
 
    Private Declare Function sum Lib "example1.dll" (ByVal x As Long, ByVal y As Long) As Long
 
End Class
Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Button1.Text = Str(sum(CInt(TextBox1.Text), CInt(TextBox2.Text)))
    End Sub
 
    Private Declare Function sum Lib "example1.dll" (ByVal x As Long, ByVal y As Long) As Long
 
End Class

but I still have that problem

Last edited by daggath; Sep 6th, 2008 at 8:18 pm. Reason: clicked on post to soon.

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dougy83

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Re: Strange DLL problem...

Sep 6th, 2008

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Originally Posted by Ancient Dragon

how did you declare it in your vb program? what you posted appears to be correct. But you don't need both the *.def file and use of _dllspec(__export) -- all you need is one of them.

You do need both the *.def file and use of _dllspec(__export) if you want clean names exported from the dll (at least in MinGW and VC++2008). Without the def file, you will export a function something like "?sum@@YGHHH@Z"; with the .def file the function name exported is "sum"

Last edited by dougy83; Sep 6th, 2008 at 8:28 pm.

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dougy83

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Re: Strange DLL problem...

Sep 6th, 2008

What language are you using to call the dll?? You said VB above (I assumed vb6), are you sure it's not VB.net or Visual Basic 2005/6/7/8?? vb6 successors have different data types to vb6 - I think long is 64bits, so use Int32 instead of long for the declare statement.

Last edited by dougy83; Sep 6th, 2008 at 8:33 pm.

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daggath

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Re: Strange DLL problem...

Sep 6th, 2008

Sorry I wasn't clear, it was visual basic 2005... I'll try your suggestion of using int32.. will update this post when I finish trying it...

Yes that worked!

Thank you very much :-)

Last edited by daggath; Sep 6th, 2008 at 8:49 pm. Reason: tested suggestion