Improving slice accuracy by compression of data and control flow paths
Proceedings of the the 7th joint meeting of the European software engineering conference and the ACM SIGSOFT symposium on The foundations of software engineering
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Design by contract is a practical methodology for evolving code together with its specification; it helps prevent many errors, and catch others close to their sources. Unfortunately, writing (and maintaining) contracts requires a non-trivial investment of time and effort. We are developing a tool, called Discern, to statically analyze existing programs and discover draft contracts for them. Discern works by propagating weakest preconditions and strongest postconditions through the code. Known pre- and postconditions of operations used in the code help refine the contract; conversely, new assertions discovered can be propagated to clients of the method being analyzed. As usual, loops make the analysis difficult; heuristics are used to recognize the most common loop forms and extract useful information about them. Discern uses a library containing specifications of the most-used language libraries. With the manual addition of one postcondition and tagging of 3 assertions as invariants, Discern computed the correct preconditions for all but one method of Java's Vector class, and similar results were obtained for StringBuffer.