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Error Calling a C++ DLL from VB 2010 .NET 4

Posted on 2011-03-21
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Last Modified: 2012-08-13
Hi Folks,

I've got a c++ DLL (written by a well knownforum member on here!). I've been using it fine with vb.net 2005, now I've upgraded to VB 2010 I get this:

A call to PInvoke function 'xxxxxxxxxx!xxxxxxxxxxx.PUX::ExecuteScript' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature.

All processes are 32 bit, which is what the dll was compiled for. I can see the *32 in process manager.

I've tried recompiling the DLL with Visual Studio 2010 - that doesnt fix it.
This is windows 2008 R2. I've seen it working with .NET 2 on Windows 2003 R2 64 bit version.

So I think its something about .net 4.

Here's the declarations:

in c++

      int ExecuteScript(BSTR Script, BSTR OutputFile, BSTR Host, BSTR User, BSTR Pass, BSTR SUUser, BSTR SUPass, unsigned int unAuthTimeout, unsigned int unFlags);


in vb:

    Private Declare Auto Function ExecuteScript _
        Lib "UXDiscovery.dll" _
        (ByVal sScript As String, ByVal sOutputFile As String, ByVal sHost As String, _
        ByVal sUser As String, ByVal sPass As String, _
        ByVal sRootUser As String, ByVal sRootPass As String, ByVal lTimeout As UInt32, ByVal lFlags As UInt32) As Int32

        Dim iReturn As Integer = ExecuteScript(sScript, sPath, IPAddress, msUserName, msPassword, "", "", lTimeout * CType(1000, UInt32), mlFlags)

These all started "As Integer", the UInt32 is just me trying different things, but nothing yet works..

thanks
Paul





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Question by:plq
3 Comments
 
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Expert Comment

by:MedievalWarrior
ID: 35182823
Change the Auto to Unicode and then pass Nothing instead of "" to the function. You can also use Integer it would just become converted to unsigned integer on the c++ end so that shouldn't make a difference. It's the BSTR strings that is most likely the problem. If the above doesn't work you may need to marshal each parameter as <bstr> using DllImport attribute.
Dim bstrNotUsed1 as String = Nothing
Dim bstrNotUsed2 as String = Nothing

' Calculate lTimeout here
Dim iReturn As Integer = ExecuteScript(sScript, sPath, IPAddress, msUserName, msPassword, bstrNotUsed1 ,bstrNotUsed2 , lTimeout , mlFlags)

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Accepted Solution

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wdosanjos earned 500 total points
ID: 35183256
Another potential issue is a Calling Convention mismatch.  Declare uses CallingConvention.StdCall and C++ has CallingConvention.Cdecl as the default.  To change the calling convention, you need to replace Declare by DllImpot as follows:

<DllImport("UXDiscovery.dll", CharSet:=CharSet.Auto, CallingConvention:=CallingConvention.Cdecl)>
Public Shared Function ExecuteScript _
	(ByVal sScript As String, ByVal sOutputFile As String, ByVal sHost As String, _
	ByVal sUser As String, ByVal sPass As String, _
	ByVal sRootUser As String, ByVal sRootPass As String, ByVal lTimeout As UInt32, ByVal lFlags As UInt32) As Int32
End Function

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I hope this helps.
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LVL 8

Author Closing Comment

by:plq
ID: 35187897
Spot on - thank you
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