Deterministic Replay Debugging of IEC 61131-3 SoftPLC programs

Determimstic Replay Debugging is an approach to finding field failures in application runs. It records an application run so that it can be replayed deterministically in a development system for debugging purposes without connection to a physical environment. In this paper, we present a solution for deterministic replay debugging of hard real-time SoftPLC applications written in the IEC 61131-3 languages. By taking advantage of the special properties of these programs and by careful engineering, our technique allows recording a SoftPLC application run with minimal overhead and obeying real-time constraints. In later phases, which are off-line, the original program run is reconstructed to be replayed for debugging. We present the conceptual basis of our approach, a tool chain including a time-traveling debugger, and an evaluation as well as an industrial case study for validating the approach.