Stack Trace in VB6

Question

Is it possible to get the stack trace information in Visual Basic 6.0. I mean I want to find out the function name and exact line that causes the error similar to .NET stack trace. I have created an ActiveX DLL which works fine in my test environment but it throws an error in production environment(error : 91-Object variable or With block variable not set). Any help on this much appreciated.

Answer 1

You may not be able to get at that in VB6. previous question.
Get as much information from the Err object.

Answer 2

The only option is to do it manually, with VB6's error handling.
Here is an example:
http://www.vbaccelerator.com/home/vb/code/Techniques/RunTime_Debug_Tracing/article.asp

Answer 3

VB6 doesn't seem to have a decent way to do that natively.

It's a bit cumbersome, but you could put together a custom solution that adds lines to a text file whenever you want it to. Put together a method somewhere that looks like this:

Public Sub LogCall(message as String)
    Open "c:\My Documents\sample.txt" For Output As #1
    Print #1, message
    Close #1
End Sub

and then manually call it from your own functions

LogCall "MyFunction: Line 42"

It doesn't solve the problem, it might help you narrow it down.

With regards to your specific error, I would go through and check situations where you're assigning an object to a variable - I find that it's easy to forget the Set keyword and get the exact same error when I least expect it.

Hope this helps. Good luck!

Answer 4

This is a good way to do it - an answer on the existing duplicate question. Use MZTools to insert the error handlers automatically

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Alternatively, you can debug your built DLL in the production environment using WinDBG, a free standalone debugger from Microsoft. Compile your DLL into native code with symbols (create PDB files).

Here's a 2006 blog post by a Microsoft guy about using Windbg with VB6, and 2004 blog post by another Microsoft guy with a brief introduction to Windbg.