FIX: Application Error in Locals Window with Specific Variables

ID: Q197193

The information in this article applies to:
  • Microsoft Visual FoxPro for Windows, versions 5.0, 5.0a

SYMPTOMS

When you do the following:

  1. Run a program that uses several variables consisting of single alpha character names.


  2. Release a form.


  3. Scroll the Debugger Locals window to look at some of the variable values.


Windows displays an application error message, and Visual FoxPro is terminated.

The message displayed depends on the operating system:

  • Under Windows NT, an error message similar to the following appears:
    An application error has occurred and an application error log is being generated.

    vfp.exe
    Exception: access violation (0xc0000005), Address 0x0043e8db
  • Under Windows 9x, an error message similar to the following appears:
    This program has performed an illegal operation and will be shut down. If the problem persists, contact the program vendor.
    If you click Details in the dialog box, a message similar to the following appears:
    VFP caused an invalid page fault in module VFP.EXE at 0137:0044940e.


STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug has been corrected in Visual FoxPro 6.0.


MORE INFORMATION

Steps to Reproduce Behavior



  1. Run the following code from a program (.prg) file: 
    
      SET STEP ON
      CLEAR DEBUGGER
      STORE .t. to a,b,c,d,e,f,g,h
      KEYBOARD "{enter}"

      TheForm=CreateObject("aForm")
      TheForm.show
      READ events
      RETURN

      DEFINE class aForm as form
         ADD object aButton as commandbutton
         PROCEDURE aButton.click
            thisform.release
         ENDPROC
      ENDDEFINE


  2. Switch to the debugger by pressing ALT+Tab.


  3. Scroll down in the Locals Window to the last item by clicking on the down arrow in the Locals Window scroll bar.


  4. The Locals window scroll bar must be visible for this behavior to occur. If you do not see the error, you can make the Locals window shorter by resizing it with the mouse, and repeating the steps.


RESULT: You will receive an application error that will vary depending on the operating system. See the SYMPTOMS section above for details. The addresses may vary depending on operating system version or Visual FoxPro 5 build number.

This only happens with these specific variable names. If you modify the STORE command in the program above to read as follows, the behavior does not occur: 

   STORE .t. to aa,bb,cc,dd,ee,ff,gg,hh
As a rule, it is a good idea to avoid the letters "A" through "N", uppercase or lowercase, for variable, field, or table names. Visual FoxPro uses these as default alias names for tables when tables are opened and their names are already in use.

Example: 

   USE table1
   USE table1 AGAIN IN 0
The second table1 will be used under the alias A.

This error does not occur if you do not scroll in the Locals window.

(c) Microsoft Corporation 1998, All Rights Reserved. Contributions by Jim Saunders, Microsoft Corporation

Additional query words:

Keywords : kbMiscTools kbVFp500abug kbVFp600fix kbXBase
Version : WINDOWS:5.0,5.0a
Platform : WINDOWS
Issue type : kbbug


Last Reviewed: August 5, 1999
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