An empirical study of the use of friends in C++ software

A commonly held belief is that the friend construct in C++ is a violation of encapsulation. However, little empirical analysis of its use has taken place to provide evidence to support this claim. This paper presents a study which assesses the design implications of including friendship in a system. A number of hypotheses are investigated based on previous work in this area by Counsell and Newson, [4]. Our initial findings suggest that classes declared as friends are coupling hotspots, that the more friends a class has the more protected and private members it will contain and that friendship is not used to access inherited protected members.