Section: New Results

Deductive Verification

• F. Bobot, J.-C. Filliâtre, C. Marché, G. Melquiond, and A. Paskevich have presented the proof session mechanism of Why3 at VSTTE 2013 [23] . It is a technique to maintain a proof session against modification of verification conditions. It was successfully used in developing more than a hundred verified programs and in keeping them up to date along the evolution of Why3 and its standard library. It also helps out with changes in the environment, e.g. prover upgrades.

• M. Clochard, C. Marché, and A. Paskevich developed a general setting for developing programs involving binders, using Why3. This approach was successfully validated on two case studies: a verified implementation of untyped lambda-calculus and a verified tableaux-based theorem prover. This work will be presented at the PLPV conference in January 2014 [29]

• M. Clochard published at the POPL conference a paper presenting a work done during an internship at Rice University (Houston, TX, USA) with S. Chaudhuri and A. Solar-Lezama [28] . It is a new technique for parameter synthesis under boolean and quantitative objectives. The input to the technique is a “sketch” — a program with missing numerical parameters — and a probabilistic assumption about the program's inputs. The goal is to automatically synthesize values for the parameters such that the resulting program satisfies: (1) a boolean specification, which states that the program must meet certain assertions, and (2) a quantitative specification, which assigns a real valued rating to every program and which the synthesizer is expected to optimize.

• J.-C. Filliâtre, L. Gondelman, and A. Paskevich have formalized the notion of ghost code implemented in Why3, in a paper The Spirit of Ghost Code [49] to be submitted. This is an outcome of L. Gondelman's M2 internship (spring/summer 2013).

• In 2013, two public releases of Why3 were launched, version 0.81 in March and version 0.82 in December [42] . A first important evolution relies on significant efficiency improvements both in terms of execution speed and of memory usage. The second major evolution is the support for many new provers, including interactive provers PVS 6 (used at NASA) and Isabelle2013-2 (planned to be used in the context of Ada program via Spark), and automated ones: CVC4, Mathematica, Metitarski, Metis, Beagle, Princess, and Yices2. The design of the programming language of Why3(WhyML) was presented during a tool demonstration at the ESOP conference [33] .