Evaluating Message Passing Control Techniques in Smalltalk

In a language like Smalltalk in which objects communicate only via message passing, message passing control is a fundamental tool for the analysis of object behavior (trace, spying) or for the definition of new semantics (asynchronous messages, proxy,...). Different techniques exist, from the well known approach based on the specialization of the doesNotUnderstand: method to the exploitation the method lookup algorithm done by the virtual machine. Until now no comparison between these techniques has been made. In this article we compare the different techniques taking into account the reflective aspects used, the scope, the limit and the cost of the control.