Cloning is a simple way to create new variants of a system. While cheap at first, it increases maintenance cost in the long term. Eventually, the cloned variants need to be integrated into a configurable platform. Such an integration is challenging: it involves merging the usual code improvements between the variants, and also integrating the variable code (features) into the platform. Thus, variant integration differs from traditional soft- ware merging, which does not produce or organize configurable code, but creates a single system that cannot be configured into variants. In practice, variant integration requires fine-grained code edits, performed in an exploratory manner, in multiple iterations. Unfortunately, little tool support exists for integrating cloned variants. In this work, we show that fine-grained code edits needed for integration can be alleviated by a small set of integration intentions-domain-specific actions declared over code snippets controlling the integration. Developers can interactively explore the integration space by declaring (or revoking) intentions on code elements. We contribute the intentions (e.g., 'keep functionality' or 'keep as a configurable feature') and the IDE tool INCLINE, which implements the intentions and five editable views that visualize the integration process and allow declaring intentions producing a configurable integrated platform. In a series of experiments, we evaluated the completeness of the pro- posed intentions, the correctness and performance of INCLINE, and the benefits of using intentions for variant integration. The experiments show that INCLINE can handle complex integration tasks, that views help to navigate the code, and that it consistently reduces mistakes made by developers during variant integration.

Many software systems are highly configurable, despite the fact that configuration options and their interactions make those systems significantly harder to understand and maintain. In this work, we consider load-time configuration options, such as parameters from the command-line or from configuration files. They are particularly hard to reason about: tracking configuration options from the point at which they are loaded to the point at which they influence control-flow decisions is tedious and error-prone, if done manually. We design and implement Lotrack, an extended static taint analysis to track configuration options automatically. Lotrack derives a configuration map that explains for each code fragment under which configurations it may be executed. An evaluation on Android apps and Java applications from different domains shows that Lotrack yields high accuracy with reasonable performance. We use Lotrack to empirically characterize how much of the implementation of Android apps depends on the platform's configuration options or interactions of these options.

We present a case study of migrating a legacy language infrastructure and its codebase to a projectional language workbench. Our subject is the generator tool ADS used for generating COBOL code for critical software systems. We decompose the ADS language into smaller sub-languages, which we implement as individual DSLs in the projectional language workbench JetBrains Meta Programming System (MPS). Our focus is on ADS' preprocessor sub-language, used to realize static variability by conditionally including or parameterizing target code. The modularization of ADS supports future extensions and tailoring the language infrastructure to the needs of individual customers. We re-implement the generation process of target code as chained model-to-model and model-to-text transformations. For migrating existing ADS code, we implement an importer relying on a parser in order to create a model in MPS. We validate the approach using an ADS codebase for handling car registrations in the Netherlands. Our case study shows the feasibility and benefits (e.g., language extensibility and modern editors) of the migration, but also smaller caveats (e.g., small syntax adaptations, the necessity of import tools, and providing training to developers). Our experiences are useful for practitioners attempting a similar migration of legacy generators to a projectional language workbench.

Highly-configurable software systems are pervasive, although configuration options and their interactions raise complexity of the program and increase maintenance effort. Especially load-time configuration options, such as parameters from command-line options or configuration files, are used with standard programming constructs such as variables and if statements intermixed with the program's implementation; manually tracking configuration options from the time they are loaded to the point where they may influence control-flow decisions is tedious and error prone. We design and implement Lotrack, an extended static taint analysis to automatically track configuration options. Lotrack derives a configuration map that explains for each code fragment under which configurations it may be executed. An evaluation on Android applications shows that Lotrack yields high accuracy with reasonable performance. We use Lotrack to empirically characterize how much of the implementation of Android apps depends on the platform's configuration options or interactions of these options.