Abstract: A local analysis analyzes the values of objects paying attention to program flow and a global analysis analyses the object independent of the flow. The local and global analysis interact to infer the invariants of objects used within a computer program. The local analysis is given the known invariants of an object by the global analysis when the object transitions from a valid to a mutable state. It then keeps track of all of the values of objects encountered until the object transitions from mutable to a valid state, when the information known to the local analysis is passed to the global analysis, which may use the new object values to add to the current list of invariants for the given object.

Abstract: Techniques and tools are described for analyzing software. For example, an analysis tool performs abstract interpretation with a congruence abstract domain and/or a heap succession abstract domain. For the congruence abstract domain, the tool tracks equivalence classes between alien expressions and base domain variables. For the heap succession abstract domain, the tool tracks updates to a heap. In either case, to preserve information after updates, the tool may identify an expression having an unreachable value then determine an equivalent expression that lacks the unreachable value.