A flat reachability-based measure for CakeML's cost semantics

Paper in proceeding, 2021

The CakeML project has recently developed a verified cost semantics that allows reasoning about the space safety of CakeML programs. With this space cost semantics, compiled machine code can be proven to have tight memory bounds ensuring no out-of-memory errors occur during execution. This paper proposes a new cost semantics which is designed to make proofs about space safety significantly simpler than they were with the original version. The work described here has been developed in the HOL4 theorem prover.