Library developers who have to evolve a library to accommodate changing requirements often face a dilemma: Either they implement a clean, efficient solution but risk breaking client code, or they maintain compatibility with client code, but pay with increased design complexity and thus higher maintenance costs over time.We address this dilemma by presenting a lightweight approach for evolving application programming interfaces (APIs), which does not depend on version control or configuration management systems. Instead, we capture API refactoring actions as a developer evolves an API. Users of the API can then replay the refactorings to bring their client software components up to date.We present CATCHUP!, an implementation of our approach that captures and replays refactoring actions within an integrated development environment semi-automatically. Our experiments suggest that our approach could be valuable in practice.

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The effectiveness of garbage collectors and leak detectors in identifying dead objects depends on the accuracy of their reachability traversal. Accuracy has two orthogonal dimensions: (i) whether the reachability traversal can distinguish between pointers and nonpointers (type accuracy), and (ii) whether the reachability traversal can identify memory locations that will be dereferenced in the future (liveness accuracy). This article presents an experimental study of the importance of type and liveness accuracy for reachability traversals. We show that liveness accuracy reduces the reachable heap size by up to 62% for our benchmark programs. However, the simpler liveness schemes (e.g., intraprocedural analysis of local variables) are largely ineffective for our benchmark runs: one must analyze global variables using interprocedural analysis to obtain significant benefits. Type accuracy has an insignificant impact on a garbage collector's ability to find unreachable objects in our benchmark runs. We report results for programs written in C, C++, and Eiffel.

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