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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 re

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-about-it-nearly.html 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.

tonyedgecombe 10y ago
I don't think Spolsky was saying their product is bug free, just that they won't tolerate having known bugs.
- bigiain 10y ago
  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.
lmm 10y ago
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.
- chimprich 10y ago
  > Provably correct software is possible. Ah cool, so you've solved the halting problem then?
  - weavie 10y ago
    They didn't say it had to be Turing complete.
    - DanWaterworth 10y ago
      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.
  - DanWaterworth 10y ago
    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.
  - lmm 10y ago
    It was "solved" in 1940 (proven in 1967) by the simply typed lambda calculus.
- jbergens 10y ago
  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...
- bennofs 10y ago
kmorgan 10y ago
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.
BurningFrog 10y ago
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.

tonyedgecombe 10y ago

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

bigiain 10y ago
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.

lmm 10y ago

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.

chimprich 10y ago
> Provably correct software is possible. Ah cool, so you've solved the halting problem then?
- weavie 10y ago
  They didn't say it had to be Turing complete.
  - DanWaterworth 10y ago
    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.
- DanWaterworth 10y ago
  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.
- lmm 10y ago
  It was "solved" in 1940 (proven in 1967) by the simply typed lambda calculus.
jbergens 10y ago
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...
bennofs 10y ago

kmorgan 10y ago

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.

BurningFrog 10y ago

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.