parameter on dlls

[SiaMeX]

I know that this will be very easy for you guys...

'==========================================================
'MY VB CODE
'==========================================================
Private Declare Sub MyFunction Lib "MyDLL.dll" (ByVal MyParameter As String) As Integer

Private Sub TestFunc ()
    MyParameter = "Original String"
    MyFunction MyParameter 
    Msgbox MyParameter        -----> string should now be
                                                  "String Overwritten"
End Sub
===========================================================

After passing thru my MyFunction, the variable (MyPrameter) should now be overwritten by that previously called function. I have my Mydll.dll code below that i think there's something missing with it. Please help my with this code.

//=========================================================
//MyDll.dll in C/C++ CODE:
//=========================================================

#include ...
     .
     .
     .
int __declspec(dllexport) CALLBACK MyFunction (LPSTR MyParameter)
{
     strcpy (MyParameter, "Sting Overwritten");
     return 0;
}
//=========================================================

thank you so much!

 

[AtomicChip]

Not 100% sure about this (I'm a little newer to C++ myself), but I believe that passing an LPSTR as a parameter passes it by val, not by reference - so, MyParameter in the c++ code would be a newly created LPSTR object based on the value of the MyParameter in the VB code (not a reference to it).

Try this:

//=========================================================
//MyDll.dll in C/C++ CODE:
//=========================================================

#include ...
     .
     .
     .
int __declspec(dllexport) CALLBACK MyFunction (LPSTR & MyParameter)
{
     MyParameter = "String Overwritten";
     return 0;
}
//=========================================================

Let me know if that does the trick (haven't tested it or anything - just the first thought off the top of my head).

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