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A Simple Debugging Guide

kenobewan
Expert 2.5K+
P: 4,871
Congratulations! You are one of the few who realise that over 80% of errors are simple and easy to fix. It is important to realise this as it can save a lot of time. Time that could be wasted making unnecessary changes, that in turn can cause further problems.

Programming is a humbling experience. An experience that causes one to reflect on human error. One major cause of these errors is syntax, syntax, syntax. We tend not to notice when we have made a typo. It is too easy to spend an hour trying to fix a problem that was caused by a typo. Accepting human error, that you made a mistake, is a reasonable first assumption.

Another important assumption to fixing problems is Occam's razor - the simpliest explanation is more often than not the best. When we initially expect a simple error we don't try to over complicate things and we are more likely to use basic techniques to trap the error; we use simple debugging procedures.

Sometimes just writing a message is enough to see what is going on. One easy technique is to trap the error in a try catch block and write the error message. Its surprizing how often this simple technique is not used.

In asp.net there is a custom errors mode remoteonly. What this does is display the exception only on the local server, but anywhere else. Other users of your application may be directed to a customized error page, while you figure out what's going on.

A very important step to avoiding errors in your application is testing. This is best done on a separate machine to the development and production servers. Even if you don't have access to a test environment this is no reason not to test. We developers are not the best testers. Get someone else or preferably a group to test, believe me you'll save time and probably money.

One of the most common errors is the 'object reference not set to an instance of an object'. Null reference errors are common too. Something, a reference or a parameter for example, is missing. So check the page references and parameters. Look in that error line to see what may be missing or null. Write any values that may be null.

A simple thing that you can do is continue to practice. Programming in an unfamiliar language is slow to start with, but experience is cumulative. As you get more practice, things like error handling become easier. It doesn't become easier if you just copy & paste all the time, there is no substitute for understanding what's going on.

There are many debugging techniques, but that is not the point of this article. Its not until I started to appreciate the number of my errors and the simplicity of fixing them, that I really started to make progress. At times I am still guilty of skipping the diagnosis and heading straight for the medicine cupboard. This has almost always been a mistake.

I hope that you avoid some of the frustrations that I have had over the years by not ignoring human error and accepting how simple steps can resolve most problems.

Happy programming!
Oct 3 '08 #1
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6 Comments


100+
P: 127
Well, thats a beautiful write up!

You are certainly right in almost all the places. Human errors are trivial and the impacts created are more.

A fact not to forget is, "We learn by mistakes" :). But we should ensure that "mistakes are NOT repeated" -- thats when we call it as an experience!

Cheers,
Raghavan alias Saravanan M.
Nov 13 '08 #2

P: 15
Thanks for the nice article. Good encouragement for beginners like me who are afraid of bugs.
there is no substitute for understanding what's going on.
This is my most favourite line of the article.
Thank you,
Rajesh V.
Dec 25 '08 #3

freelance programmer
P: 11
What I have found is keeping a note of what all steps you took , what all did you observe also help a lot to debug difficult bugs.
Feb 23 '09 #4

Expert 5K+
P: 8,434
Hi.

I'd just like to point out what (ironically) looks like a typo in the article. To quote...

In asp.net there is a custom errors mode remoteonly. What this does is display the exception only on the local server, but anywhere else.
At a guess, there's a "not" missing there.
Feb 26 '09 #5

prasanxxx
P: 2
thats so kind of you to make newbie's like me comfortable in programming.
sumtimes the problem is gruesome but at the most its due to simple things only
Apr 17 '09 #6

100+
P: 344
I was stopped for nearly three or four days in a program to count objects with specific color in an image, I did the whole code without change in approximately two hours but didn't work, after three days of just looking for what I have done wrong was a property that returns a different field's value (simply int).

It wasn't believable to me in first that I can fix a problem, It disappeared with some try and encourage thoughts like this.

Thanks, It was a nice article encourages much.
Jun 3 '09 #7