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Software Product Lines (SPLs) play an essential role in contemporary software development, improving program quality and reducing the time to market. However, despite its importance, several questions concerning SPL dependability did not get enough attention yet, such as: how the exception handling code has been implemented in SPLs? The characteristics of the exception handling code may lead to faulty SPL products? The Exception Handling (EH) is a widely used mechanism for building robust systems and is embedded in most of mainstream programming languages. In SPL context we can find exception signalers and handlers spread over code assets associated to common and variable SPL features. If exception signalers and handlers are added to a SPL in an unplanned way, products can be generated on which variable features may signal exceptions that remain uncaught or are mistakenly caught by common features or other variable features. This paper describes an empirical study that categorizes the possible ways exceptions flow through SPL features and investigates whether some of their characteristics can lead to faulty exception handling behavior. The study outcomes presented in this paper are helpful in several ways, such as: (i) enhancing the general understanding of how exceptions flow through mandatory and variable features; (ii) providing information about the potential problems related to specific kinds of flows detected in this study; and (iii) presenting how a static analysis tool can be used to support the identification of potentially faulty exception handling flows.

Despite being an old language feature, Java exception handling code is one of the least understood parts of many systems. Several studies have analyzed the characteristics of exception handling code, trying to identify common practices or even link such practices to software bugs. Few works, however, have investigated exception handling issues from the point of view of developers. None of the works have focused on discovering exception handling guidelines adopted by current systemswhich are likely to be a driver of common practices. In this work, we conducted a qualitative study based on semi-structured interviews and a survey whose goal was to investigate the guidelines that are (or should be) followed by developers in their projects. Initially, we conducted semi-structured interviews with seven experienced developers, which were used to inform the design of a survey targeting a broader group of Java developers (i.e., a group of active Java developers from topstarred projects on GitHub). We emailed 863 developers and received 98 valid answers. The study shows that exception handling guidelines usually exist (70%) and are usually implicit and undocumented (54%). Our study identifies 48 exception handling guidelines related to seven different categories. We also investigated how such guidelines are disseminated to the project team and how compliance between code and guidelines is verified; we could observe that according to more than half of respondents the guidelines are both disseminated and verified through code inspection or code review. Our findings provide software development teams with a means to improve exception handling guidelines based on insights from the state of practice of 87 software projects.

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