FIX: COM Servers Cannot Redimension Arrays Passed By Reference

ID: Q221720

The information in this article applies to:

Microsoft Visual FoxPro for Windows, versions 5.0, 5.0a, 6.0

SYMPTOMS

You pass an array by reference to a method of a COM server built in Visual FoxPro. The method redimensions the array. If you call the method from a Visual FoxPro 6.0 client and use the COMARRAY function, you may see the following error:

OLE IDispatch exception code 302 from Visual FoxPro for Windows: Data type mismatch...

If you call the method from a Visual FoxPro 5.0 client, or a Visual FoxPro 6.0 client not using the COMARRAY function, you may not see an error, but instead the array will not be redimensioned, and the array's original contents remain unchanged. From clients other than Visual FoxPro, you may see the earlier behaviors, or other variations.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.

This bug has been fixed in Visual Studio 6.0 Service Pack 3.

MORE INFORMATION

Steps to Reproduce Behavior

Create a new project called Arraytest.

Add a new program to the project.

Paste the following code into the program:


   DEFINE CLASS arraydim AS CUSTOM OLEPUBLIC
      cVerStr = VERSION()
      PROCEDURE GetArray(taArray, tnRows)
         IF PARAMETERS() < 2
            tnRows = ALEN(taArray)
         ENDIF
         LOCAL lni
         DIMENSION taArray[tnRows]
         FOR lni = 1 TO ALEN(taArray)
            taArray[lni] = lni
         ENDFOR
         RETURN
      ENDPROC
   ENDDEFINE

Save the program as Arraytest.prg.

Build the project into a COM DLL.

Run the following code from a program (.prg) file:


   CLEAR
   CLEAR ALL
   LOCAL ARRAY laArray[5]
   LOCAL OX
   ox = CREATEOBJECT('arraytest.arraydim')
   * =COMARRAY(ox,11)
   STORE 'X' to laArray
   ?'Value of first element',laArray[1]
   ?'Array length before', ALEN(laArray)
   ox.GetArray(@laArray, 10)
   RELEASE ox
   ?'Array length after', ALEN(laArray)
   ?'Value of first element',laArray[1]

From a Visual FoxPro 5.0 client (this must be done with the COMARRAY function removed) the array length and value of the first element are unchanged. From a Visual FoxPro 6.0 client, using the COMARRAY function, the error listed in SYMPTOMS will occur. From a Visual FoxPro 6.0 client not using the COMARRAY function, the behavior is the same as that under Visual FoxPro 5.0.

REFERENCES

Additional query words:

Keywords : kbCOMt kbVFp500abug kbVFp600bug kbVS600sp3fix kbGrpFox kbDSupport
Version : WINDOWS:5.0,5.0a,6.0
Platform : WINDOWS
Issue type : kbbug