bugs

[David Vaughan]

On 10/04/2006, at 2:37, Geoff Canyon wrote:

> The question is this: what do you think is the upper limit for  
> _completely_ bug-free code?

Was your code bug-free the first time you wrote it, no typographic  
errors or any other changes? Do not answer that because it is only a  
lead-in to the next comment, that the upper limit is for code which  
can be made bug free with reasonable economic effort, and that is in  
my view controlled by the number of people involved.

Your script worked well because you (I presume) conceived the  
requirement, the design and the implementation and it was self- 
documenting in that the descriptive text carries import to you which  
it may not for other people. I take it for the moment that you are  
also the user.

To the extent that you introduce new actors at any one of those five  
roles, you will increase the probability of bugs both arising and  
persisting.

I have some small to complex stacks which to the best of my knowledge  
are bug free, but no-one else uses them, they are substantially  
undocumented, and the design and usage pattern are perfectly matched,  
both being through me. I have little doubt that use by other people  
might expose real bugs and absolutely no doubt whatsoever that those  
other users would raise as bugs points which I considered to be  
"obvious" design choices or usages.

I have also a fairly complex stack with at least one obvious bug but  
I know about it and work around it because that costs me less effort,  
even on a regular basis, than investing in fixing that stack compared  
with my other development priorities which are themselves way below  
my other life priorities (reiterating for those who have not read it  
before that I do not develop software to order nor for product).  
Eventually, it will irritate me enough and I will have the spare time  
so I will fix it.

The last part was a bit of a digression. The main answer is that bugs  
arise less from code size than from the count of actors in the five  
steps from concept to use. A sufficiently complex project conceived,  
developed and used by a single person will merely not be finished  
while the development bugs are being ironed out. :-)

cheers
David