Question

A VB6 app is experiencing a run-time errors at a variety of places.

I know this is the result of poor error handling, but is it possible to analyse the code to see where it is susceptible to run-time errors?

Answer 1

You need to make sure that every one of the methods (functions, subs, properties…) in your code base has an error handling statement. It’s probably true that not every single one can generate a run time error, but that will protect the application from crashing without a lot of upfront analysis.

Make sure there’s a statement before any executable line of code that says “On Error GoTo…” with a label, and then make sure to put that label with some error handling code at the bottom of the method. I’ve used a free tool called MZ-Tools 3.0 that allows you to automate the inclusion of this text. There is an Error Handler tab in the options that lets use specify what text you want to put in and where. This is what mine looks like:

    On Error GoTo l{PROCEDURE_NAME}_Error

    {PROCEDURE_BODY}

    Exit {PROCEDURE_TYPE}

l{PROCEDURE_NAME}_Error:

    LogError "{MODULE_NAME}", "{PROCEDURE_NAME}", Err, Err.Description

Then I just make sure that the LogError function exists and writes the error out to a log file that I can review.