CompCertS: A Memory-Aware Verified C Compiler Using a Pointer as Integer Semantics

The CompCert C compiler provides the formal guarantee that the observable behaviour of the compiled code improves on the observable behaviour of the source code. In this paper, we present a formally verified C compiler, CompCertS , which is essentially the CompCert compiler, albeit with a stronger formal guarantee: it gives a semantics to more programs and ensures that the memory consumption is preserved by the compiler. CompCertS is based on an enhanced memory model where, unlike CompCert but like Gcc , the binary representation of pointers can be manipulated much like integers and where, unlike CompCert , allocation may fail if no memory is available. The whole proof of CompCertS is a significant proof-effort and we highlight the crux of the novel proofs of 12 passes of the back-end and a challenging proof of an essential optimising pass of the front-end.