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Comment by bigiain | Hacker News Reader

There is an old Joel On Software blog post I was reading recently that talked about a methodology at Microsoft they called "Zero defects", where fixing known bug _alway_ had priority over working on new features.

Here - pont 5 in this post: http://www.joelonsoftware.com/articles/fog0000000043.html

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Interesting. I recently read an article[1] where John Romero talks about the culture of early id Software and he mentions something similar:

> As soon as you see a bug, you fix it. Do not continue on. If you don’t fix your bugs your new code will be built on a buggy codebase and ensure an unstable foundation.

Looking back to the codebases i've worked with, this advice seems extremely wise.

[1] http://www.gamasutra.com/view/news/279357/Programming_princi...

I guess he forgot about this when making Daikatana? :-) Good advice nonetheless. It's a bit far-fetched, but reminds me of the "if you can do it in less than fives minutes, do it now" thing.

Obligatory mention of 'Masters of Doom'. I think Romero may have been a better programmer than first-time large project manager, but he wouldn't be the only one :)

That's exactly what "Lean" is all about. When you spot an issue "pull the Andon cord" and stop the line, deal with the issue then and there. You then potentially conduct Kaizen to address the process to ensure the issue doesn't happen again.

At core all of Agile Software Development is aiming to mirror Lean in the manufacturing world. At the core of which is the concept of minimizing work-in-progress. Because WIP may result in waste if you subsequently find a problem that renders the WIP null and void. Hence the drive for continuous flow to minimize WIP and a "stop the line" mentality to spot and address issues when they arise.

I'm often amazed at how many people "doing" agile through sprints don't understand that the sprint is just an artificial mechanism to minimize WIP.

Not dealing with technical debt when it occurs is just increasing WIP.

That's by far the best way to work.

It's hard to explain to someone who hasn't experienced it how much easier it is to develop in a bug free code base.

I challenge that; I don't think a "bug free code base" actually exists. Joshua Bloch has a great article about this which I think may be of interest to other readers: https://research.googleblog.com/2006/06/extra-extra-read-all....

To paraphrase: We programmers need all the help we can get, and we should never assume otherwise. Careful design is great. Testing is great. Formal methods are great. Code reviews are great. Static analysis is great. But none of these things alone are sufficient to eliminate bugs: They will always be with us. A bug can exist for half a century despite our best efforts to exterminate it. We must program carefully, defensively, and remain ever vigilant.

I don't think Spolsky was saying their product is bug free, just that they won't tolerate having known bugs.

Not even quite "won't tolerate having known bugs" - it's fundamentally acknowledging that you will at times find bugs in your code base - but that when you do discover bugs you'll prioritise fixing them above adding new features or hitting pre-set project deadlines.

It's a great philosophy or methodology, but it can be very hard to execute on 100%. In the real world there are deadlines and resource requirements and impatient clients and produce launch plans with set dates and trade shows starting next week and the Thanksgiving/Xmas launch opportunity and and and.

There exist, however, code bases where any refactoring or feature addition exposes a latent bug that has to be fixed before proceeding. Additionally, fixing that bug often exposes another one.

We didn't have a bug free code base, but it was rare that someone found an actual bug. As I remember it, it happened maybe once or twice a month in an 8 person team.

At other places I've worked, I wouldn't raise an eyebrow if I found 3 bugs in a day, just trying to get other stuff done.

That bug exists because it's written in a language where + is permitted to silently do surprising things, for reasons that made sense as a performance optimization for general-purpose computers in the '70s and embedded systems in the '90s (the original target of Java) but do not make sense for general-purpose computers today.

Better languages are possible. Provably correct software is possible. We really can eliminate bugs.

> Provably correct software is possible.

Even then, the software is provably correct according to some specification, which can still have bugs. No technology can fully prevent logic bugs.

You're technically correct, but in practice, proving that software does confirm to a formal specification is, empirically, a good way of drastically reducing defects.

Often when people mention provably correct software what they mean is software that don't crash and always produces output for correct input. It usually doesn't mean that the output is correct...

> Provably correct software is possible.

Ah cool, so you've solved the halting problem then?

You don't need to solve the halting problem to write provably correct software (that is, software that conforms to a formal specification). The halting problem (and Rice's theorem) come into play when you are trying to deduce things about arbitrary programs written in turing complete languages.

It's like the difference between being able to express proofs in maths, versus having a method of deciding the validity of arbitrary propositions. We can certainly write programs that we can we can prove things about, but given an arbitrary program, we can't always tell whether it will do the right thing.

It was "solved" in 1940 (proven in 1967) by the simply typed lambda calculus.

They didn't say it had to be Turing complete.

It's not about turing completeness. Deducing arbitrary properties of programming written in primitive recursive languages is also undecidable. This is why type inference in dependently typed languages is undecidable.

Also Joel wrote another article where he says that rewriting the code from scratch (removing technical debt or switching to a new popular framework) is generally a bad idea: http://www.joelonsoftware.com/articles/fog0000000069.html

Improving and perfecting the code is a task that can take infinite amount of time.

I like this policy, but it doesn't directly help to reduce the technical debt.

I want to believe we can someday gave the same policy for bad abstractions.

Bad abstractions are what really makes code difficult to maintain in my opinion.

And what allows many of those bugs to exist in the first place. The best interface is one which cannot be used incorrectly.

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