[Mastering-perl] Debugging, Profiling, and Cleaning Up Code

[Adrian Howard]

On 7 Oct 2006, at 11:46, brian d foy wrote:
[snip]
> I've added a bunch of stuff to the Debugging chapter:
>
> http://www.pair.com/~comdog/mastering_perl/Chapters/04.debugger.html

I kinda expected the print/warn section to move on to a discussion of  
logging modules, does that happen elsewhere? If not that would be  
trez useful. Pretty much everybody I encounter has some mastery of  
the print-style of debugging. Far fewer have any idea how to do  
logging well.

I'd stick in a warning about the problems with $SIG{ __DIE__ } and  
$SIG{ __WARN__ } and persistent environments like mod_perl.

fatalsToBrowsers - I'm in the "don't do this on live boxes" school  
since if you do have a bug it might reveal bad things to evil folk.  
Maybe worth warning folk of potential dangers?

> And I think I'm mostly done with the Profiling chapter:
>
> http://www.pair.com/~comdog/mastering_perl/Chapters/06.profiling.html

I'd appreciate a little more emphasis on the dangers of unnecessary  
optimisation near the start. I've seen people misuse Devel::SmallProf  
- spending days agonising over two or three "slow" lines that make no  
damn difference to anything.

With Devel::Cover - might be worth mentioning Module::Build's built  
in support for ./Build testcover.

POD coverage modules?

Memory profiling? - Devel::Size, Devel::Size::Report, Devel::DumpSizes ?

> Next up is the Cleaning Up Code chapter, which need the last half
> written. That's all Perl::Critic stuff:
>
> http://www.pair.com/~comdog/mastering_perl/Chapters/ 
> 07.cleaning_up_code.html

Nice apart from:

"In general, I recommend turning off warnings once a program is in  
production. Turn on warnings when you need to test or debug the  
program, but after that, you don't need them. The warnings will just  
fill up log files."

which I consider.... odd advice :-) The point of log files is to spot  
problems. Warnings are often indications of problems. That's why log  
files filling up with warnings is a /good/ thing. That way you can  
fix the problem!

Cheers,

Adrian