Towards a Model Checking Framework for a New Collector Framework

Garbage collectors provide memory safety, an important step toward program correctness. However, correctness of the collector itself can be challenging to establish, given both the style in which such systems are written and the weakly-ordered memory accesses of modern hardware. One way to maximize benefits is to use a framework in which effort can be focused on the correctness of small, modular critical components from which various collectors may be composed. Full proof of correctness is likely impractical, so we propose to gain a degree of confidence in collector correctness by applying model checking to critical kernels within a garbage collection framework. We further envisage a model framework, paralleling the framework nature of the collector, in hope that it will be easy to create new models for new collectors. We describe here a prototype model structure, and present results of model checking both stop-the-world and snapshot-at-the-beginning concurrent marking. We found useful regularities of model structure, and that models could be checked within possible time and space budgets on capable servers. This suggests that collectors built in a modular style might be model checked, and further that it may be worthwhile to develop a model checking framework with a domain-specific language from which to generate those models.