Reliability and maintainability related software coupling metrics in C++ programs

This paper describes some difficulties that one encounters in the testing and maintenance of C++ programs, which may result in program unreliability. Inheritance and polymorphism are key concepts in objectoriented programming (OOP), and are essential for achieving reusability and extendibility, but they also make programs more difficult to understand. We have tried to show by arguments and by some empirical evidence that widely used complexity metrics like lines of code, cyclomatic complexity, and Software Science’s metrics may not be appropriate to measure the complexity of C++ programs and those written in other objectoriented languages, since they do not address concepts like inheritance and encapsulation, apart from having other weaknesses. Some measures using a notion from the world of functional decomposition coupling, are defined for C++ programs. Two of them CC and AMC and equivalent ones for the three widely used complexity metrics (for comparison) are computed for five C++ programs. Our preliminary results show that our coupling measures correlate better with difficulty of testing and maintenance than the three widely used complexity metrics.