A Study on Behavioral Backward Incompatibility Bugs in Java Software Libraries

摘要

Nowadays, due to the frequent technological innovation and market changes, software libraries are evolving very quickly. To make sure that existing client software applications are not broken after a library update, backward compatibility has always been one of the most important requirements during the evolution of software platforms and libraries. However, due to various reasons, backward compatibility is seldom fully achieved in practice, and many relevant software failures are reported. Therefore, it is important to understand the status, major reasons, and impact of backward incompatibilities in real world software. Previous studies on this topic mainly focus on API signature changes between consecutive versions of software libraries, but behavioral changes of APIs with untouched signatures are actually more dangerous and are causing most realworld bugs because they cannot be easily detected. This paper presents an empirical study on 126 real-world software bug reports on backward incompatibilities of software libraries. We find that 67% of fixed client bugs caused by backward incompatibilities in software libraries are fixed by client developers, through several simple change patterns made to the backward incompatible API invocations.