Cogent: Accurate Theorem Proving for Program Verification

Many symbolic software verification engines such as Slam and ESC/Java rely on automatic theorem provers. The existing theorem provers, such as Simplify, lack precise support for important programming language constructs such as pointers, structures and unions. This paper describes a theorem prover, Cogent, that accurately supports all ANSI-C expressions. The prover's implementation is based on a machine-level interpretation of expressions into propositional logic, and supports finite machine-level variables, bit operations, structures, unions, references, pointers and pointer arithmetic. When used by Slam during the model checking of over 300 benchmarks, Cogent's improved accuracy reduced the number of Slam timeouts by half, increased the number of true errors found, and decreased the number of false errors.