Issue #5696 has been reported by Charles Nutter.

----------------------------------------
Bug #5696: rexml BaseParser uses instance_eval unnecessarily on listener add
http://redmine.ruby-lang.org/issues/5696

Author: Charles Nutter
Status: Open
Priority: Normal
Assignee: 
Category: lib
Target version: 1.9.3
ruby -v: trunk


In add_listener in REXML::BaseParser, there's code to instance eval and replace the old "pull" method with a new one that calls all listeners. I assume this was done to avoid the cost of calling .each on the listeners when there's none registered, but when the list is empty this call is nearly a no-op anyway. The singletonizing effect of instance_eval and the redefinition of #pull, on the other hand, cause a cache flush throughout the system.

I have created a patch that removes the instance_eval, initializes the listeners array unconditionally, and does the event #each unconditionally. It passes all tests, and should perform better because it's not damaging the cache.

https://gist.github.com/1420383

This can be safely backported to any Ruby version and has no visible behavior change.


-- 
http://redmine.ruby-lang.org