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Rightly or wrongly, I use the debugger. I use it all the time to step through code that I have inherited. Along the way I have run across a few debugger idioms that have been invaluable to my code archiology.

Please respond and share your debugger idioms!

  • Write intermediate data to a file
  • In some cases, while debugging, it is helpful to capture an intermediate data structure for reference. I find this particularly useful for dumping out xml content that is generated.

    DB<3> open FH, ">/tmp/foo.txt"; DB<4> print FH "THIS IS AN EXAMPLE"; DB<5> print FH $user_id; DB<6> close FH
  • Step into an expression
  • You can evaluate any valid perl expression with x while in the debugger. However you can also step into that expression using s. For example:

    DB<6> s $profile->to_xml() main::((eval 35)[/usr/lib/perl5/5.6.1/perl5db.pl:1521]:3): 3: $profile->to_xml(); DB<<7>>

    At this point, you will be stepping through the expression that was entered on the previous line.

  • break the debugger from code
  • Put the following expression somewhere in your code, run it in the debugger and the debugger will stop on the line immediately following it.

    $DB::single = 1;

There are many more debugger idioms out there, what are yours?

Hazah! I'm Employed! (But still looking...)


In reply to Neat Debugger tricks by osunderdog

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