Extended static checking: Difference between revisions

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'''Extended static checking''' ('''ESC''') is a collective name for a range of techniques for [[static code analysis|statically checking]] the correctness of various program constraints<ref>C. Flanagan, K.R.M. Leino, M. Lillibridge, G. Nelson, J. B. Saxe and R. Stata. "Extended static checking for Java". In ''Proceedings of the Conference on Programming Language Design and Implementation'', pages 234--245, 2002. doi: http://doi.acm.org/10.1145/512529.512558</ref>. ESC can be thought of as an extended form of [[Type checking|type checking]]. As with type checking, ESC is performed automatically at [[compile time]] (i.e. without human intervention). This distinguishes it from more general approaches to the [[formal verification]] of software, which typically rely on human-generated proofs. Furthermore, it promotes practicality over completeness, in that it aims to dramatically reduce the number of ''false positives'' (overestimated errors that aren't real errors, that is, ESC over strictness) at the cost of introducing some ''false negatives'' (real ESC underestimation error, but that need no programmer's attention, or aren't targeted by ESC)<ref name=GNESCUWCSC /><ref>Calysto: Scalable and Precise Extended Static Checking, Domagoj Babic and Alan J. Hu. In Proceedings of the International Conference on Software Engineering (ICSE), 2008. doi: http://dx.doi.org/10.1145/1368088.1368118</ref>. ESC can identify a range of errors which are currently outside the scope of a type checker, including [[division by zero]], [[bounds checking|array out of bounds]], [[integer overflow]] and [[Null pointer|null dereferences]].

The techniques used in extended static checking come from various fields of [[Computer Science]], including [[static analysis]], [[symbolic simulation]], [[model checking]], [[abstract interpretation]], [[satisfiability modulo theories|SAT solving]] and [[automated theorem proving]] and [[type checking]]. One characteristic is that ESC is generally performed only at an intraprocedural level (rather than an interprocedural one) applied modularly, which makes ESC be able to scale as it makes [[Design by contract]] allowed in such program (with some effort modular soundness can be achieved in some cases by making restrictions in program source code<ref name=GNESCUWCSC>{{Cite web