Hi all,

Is there a way to clear the event queue and the stack?

I have a communication program where I am several sub routines deep and
in the event of an error on the other end, I need to keep the program
from returning to all the subs. I could write a ton of code to do this,
but I really would like to simply clear the queue.

Bill

On 18 Oct 2005 01:21:31 -0700, theycallmeb***@gmail.com wrote:

I think that you'll find that  On Error does just that

On Error Resume Next
Call SomeDodgyStuff
If Err Then   ' we land up here

Try this :-

Option Explicit

Private Sub Command1_Click()
  On Error Resume Next
  Call SomeDodgyStuff
  If Err Then MsgBox "Some Error"
End Sub

Private Sub SomeDodgyStuff()
   Dim A$, B$, C$
   Me.Print "Enter SomeDodgyStuff"
   Call SomeDodgyStuffA
   Me.Print "Leave SomeDodgyStuff"
End Sub

Private Sub SomeDodgyStuffA()
   Dim A$, B$, C$
   Me.Print "Enter SomeDodgyStuffA"
   'Error 99  ' Uncomment this
   Me.Print "Leave SomeDodgyStuffA"
End Sub

As you can see, the call stack is unwound without execution

I strongly suggest that you implement error handling at lower levels
then turn it off and 'manually' raise an error if you want to jump
straight back out.

Also use Err.Clear on a good exit (which might not be as 'good')

eg:

Private Sub SomeDodgyStuff()
   Dim A$, B$, C$
   Me.Print "Enter SomeDodgyStuff"
   On Error Resume Next

   DoSomething

   If Err = 123 Then  ' Known Error
      On Error GoTo 0
      Error 99  ' Skip Out
   End If 

   If Err Then
      MsgBox "Unexpected Error"
      Err.Clear
   End If

   ' Good Exit  
   Me.Print "Leave SomeDodgyStuff"
End Sub

Personally I'm not to happy with this Throw and Catch stuff as it can
lead to 'unexpected' errors getting disguized
- but sometimes it is necessary  ...

To unwind the stack, just raise an exception that's handled by a procedure
near the root of your stack. Reserve a dedicated error code for this
purpose, e.g.

Public Const ERR_UNWIND As Long = vbObjectError OR 1000

When necessary, raise this using something like:

    Err.Raise  ERR_UNWIND, TypeName(Me), "Unwinding stack"

In all your local error handlers, test for this explicit error code. If
that's the one then re-throw the error, else handle it as per normal, e.g.

LocalErrHandler:
    If Err.Number = ERR_UNWIND Then
        ' Re-raise the error for someone else to handle
        Err.Raise Err.Number, Err.Source, Err.Description, Err.HelpFile,
Err.HelpContext
    Else
        ...handle the error as per normal...
    End If

That reserved error code will eventually find its way to your root
procedure, at which point your stack will have been reset as requested

            Tony Proctor

<theycallmeb***@gmail.com> wrote in message
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