Calling a win 32 C Library function from a VB 6.0 dll crashes

Question

I have a C Library Cdll.dll which has the function

int _stdcall AddVersion(int repval) 
{
    return (repval + 10);
}

I am calling this AddVersion function from a VB dll.

Private Declare Function AddVersion Lib "cdll.dll" (ByVal Repval As Integer) As Integer
...

Public Function VbMessageHandler(ByRef intVal As Integer) As Integer
   intVal = AddVersion(10)
End Function

I am calling this VB dll from a C dll by creating a COM wrapper for the VB dll.

ret = ObjVbclass->VbMessageHandler(&IntegerValue);

when I use this VBWrapper dll in my C exe application, it crashes by throwing Runtime exception.

Answer 1

Your declaration is wrong. A VB6 Integer is 16-bits for historical reasons, a C int is 32-bits. Use Long instead.

Private Declare Function AddVersion Lib "cdll.dll" (ByVal Repval As Long) As Long