Re: Debug code out of production systems

in reply to Debug code out of production systems

This is really easy to achive. perl will optimize away sections enclosed in if blocks with constant conditions:

$ perl -MO=Deparse -le '
> sub DEBUG () { 1 }
> if(DEBUG) { print "Debug" }
> print "Done";
> '
BEGIN { $/ = "\n"; $\ = "\n"; }
do {
    print 'Debug'
};
print 'Done';
-e syntax OK

$ perl -MO=Deparse -le '
> sub DEBUG () { 0 }
> if(DEBUG) { print "Debug" }
> print "Done";
> '
BEGIN { $/ = "\n"; $\ = "\n"; }
'???';
print 'Done';
-e syntax OK
[download]

So with a false constant, perl will replace the if with a statement B::Deparse doesn't like (but is probably a noop). With a true constant, it gets enclosed in a do block (in case there are any lexicals declared--perl doesn't look ahead far enough to know).

(And I say 'perl', not 'Perl', because it's possible that a different implementation of Perl, should there ever be one (Ponie?), may apply different optimizations.)

----
I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
-- Schemer

: () { :|:& };:

Note: All code is untested, unless otherwise stated

In Section Meditations