Item9127: CompareRevisionsAddOn should call HTML::Element->delete to avoid memory leaks

Priority:	CurrentState:	AppliesTo:	Component:	WaitingFor:
Normal	Closed	Extension	CompareRevisionsAddOn

HTML::Element documentation states:

$h->delete()

Detaches this element from its parent (if it has one) and explicitly destroys the element and all its descendants. The return value is undef.

Perl uses garbage collection based on reference counting; when no references to a data structure exist, it's implicitly destroyed -- i.e., when no value anywhere points to a given object anymore, Perl knows it can free up the memory that the now-unused object occupies.

But this fails with HTML::Element trees, because a parent element always holds references to its children, and its children elements hold references to the parent, so no element ever looks like it's not in use. So, to destroy those elements, you need to call $h->delete on the parent.

Foswiki::Contrib::CompareRevisionsAddOn::Compare::compare should call this method to avoid memory leaks. It's not a problem in CGI environment, but users may be using some persistent environment, like FastCGI or mod_perl.

-- GilmarSantosJr - 08 Jun 2010

Since _getTree returns a non-root element, it's needed to navigate to it before calling delete() method.

-- GilmarSantosJr - 08 Jun 2010