No abstract

No abstract

Reasoning about object-oriented programs requires an appropriate technique to reflect a fundamental "general relativity" property of the approach: every operation is relative to a current object, which changes with every qualified call; such a call needs access to the context of the client object. The notion of negative variable, discussed in this article, provides a framework for reasoning about OO programs in any semantic framework. We introduce a fundamental rule describing the semantics of object-oriented calls, its specific versions for such frameworks as axiomatic (Hoare-style) logic and denotational semantics, and its application to such problems as alias analysis and the consistency of concurrent programs. The approach has been implemented as part of a verification environment for a major object-oriented language and used to perform a number of proofs and analyses.

Null pointer dereferencing remains one of the major issues in modern object-oriented languages. An obvious addition of keywords to distinguish between never null and possibly null references appears to be insufficient during object initialization when some fields declared as never null may be temporary null before the initialization completes. This work identifies the key reasons of the object initialization problem. It suggests scenarios and metrics to be used as the benchmarks to compare solutions of this problem. Finally, it demonstrates application of the benchmarks on the proposed solution for object initialization in Eiffel. The article is published in the author's wording.