The Abstract Domain of Segmented Ranking Functions


We present a parameterized abstract domain for proving program termination by abstract interpretation. The domain automatically synthesizes piecewise-defined ranking functions and infers sufficient conditions for program termination. The analysis uses over-approximations but we prove its soundness, meaning that all program executions respecting these sufficient conditions are indeed terminating.

The abstract domain is parameterized by a numerical abstract domain for environments and a numerical abstract domain for functions. This parameterization allows to easily tune the trade-off between precision and cost of the analysis. We describe an instantiation of this generic domain with intervals and affine functions. We define all abstract operators, including widening to ensure convergence.

The analysis does not rely on assumptions about the structure of the analyzed program: for example, it is not limited to simple loops.

To illustrate the potential of the proposed framework, we have implemented a research prototype static analyzer, for a small imperative language, that yielded interesting preliminary results.

­čç«­čç╣ Universit├á degli Studi di Udine, Italy