Something I don't understand on chkpass.sgml

I'm currently translating chkpass.sgml and I'm having problems with this
sentence :
  This is currently a stub that does nothing.

According to answers.com, a stub is a "A small software routine placed
into a program that provides a common function." So the sentence itself
is understandable but I don't understand what "the stub" refers to in
this paragraph : the error code routine ? the comparison one ? the cast
one ?

Thanks for any pointers.

Regards.


--
Guillaume.
 http://www.postgresqlfr.org
 http://dalibo.com