Identifying reusable functions in code using specification driven techniques

The work described in this thesis addresses the field of software reuse. Software reuse is widely considered as a way to increase the productivity and improve the quality and reliability of new software systems. Identifying, extracting and reengineering software. components which implement abstractions within existing systems is a promising cost-effective way to create reusable assets. Such a process is referred to as reuse reengineering. A reference paradigm has been defined within the RE(^2) project which decomposes a reuse reengineering process in five sequential phases. In particular, the first phase of the reference paradigm, called Candidature phase, is concerned with the analysis of source code for the identification of software components implementing abstractions and which are therefore candidate to be reused. Different candidature criteria exist for the identification of reuse-candidate software components. They can be classified in structural methods (based on structural properties of the software) and specification driven methods (that search for software components implementing a given specification).In this thesis a new specification driven candidature criterion for the identification and the extraction of code fragments implementing functional abstractions is presented. The method is driven by a formal specification of the function to be isolated (given in terms of a precondition and a post condition) and is based on the theoretical frameworks of program slicing and symbolic execution. Symbolic execution and theorem proving techniques are used to map the specification of the functional abstractions onto a slicing criterion. Once the slicing criterion has been identified the slice is isolated using algorithms based on dependence graphs. The method has been specialised for programs written in the C language. Both symbolic execution and program slicing are performed by exploiting the Combined C Graph (CCG), a fine-grained dependence based program representation that can be used for several software maintenance tasks

"Bagatelle in C arranged for VDM SoLo"

This paper sketches a reverse engineering discipline which combines formal and semi-formal methods. Central to the former is denotational semantics, expressed in the ISO/IEC 13817-1 standard specification language (VDM-SL). This is strengthened with algebra of pro- gramming, which is applied in “reverse order” so as to reconstruct formal specifications from legacy code. The latter include code slicing, a “shortcut” which trims down the complexity of handling the formal semantics of all program variables at the same time. A key point of the approach is its constructive style. Reverse calculations go as far as absorbing auxiliary variables, introducing mutual recursion (if applicable) and reversing semantic denota- tions into standard generic programming schemata such as cata/paramorphisms. The approach is illustrated for a small piece of code already studied in the code-slicing literature: Kernighan and Richtie’s word count C programming “bagatelle”.FC

GamaSlicer : an online laboratory for program verification and analysis

In this paper we present the GamaSlicer tool, which is primarily a semantics-based program slicer that also offers formal verification (generation of verification conditions) and program visualization functionality. The tool allows users to obtain slices using a number of different families of slicing algorithms (\precond-based, \postcond-based, and specification-based), from a correct software component annotated with pre and postconditions (contracts written in JML-annotated Java). Each family in turn contains algorithms of different precision (with more precise algorithms being asymptotically slower). A novelty of our work at the theoretical level is the inclusion of a new, much more effective algorithm for specification-based slicing, and in fact other current work at this level is being progressively incorporated in the tool. The tool also generates (in a step-by-step fashion) a set of verification conditions (as formulas written in the SMT-lib language, which enables the use of different automatic SMT provers). This allows to establish the initial correctness of the code with respect to their contracts.Fundação para a Ciência e a Tecnologia (FCT

Statechart Slicing

The paper discusses how to reduce a statechart model by slicing. We start with the discussion of control dependencies and data dependencies in statecharts. The and-or dependence graph is introduced to represent control and data dependencies for statecharts. We show how to slice statecharts by using this dependence graph. Our slicing approach helps systems analysts and system designers in understanding system specifications, maintaining software systems, and reusing parts of systems models

Understanding object-oriented source code from the behavioural perspective

Comprehension is a key activity that underpins a variety of software maintenance and engineering tasks. The task of understanding object-oriented systems is hampered by the fact that the code segments that are related to a user-level function tend to be distributed across the system. We introduce a tool-supported code extraction technique that addresses this issue. Given a minimal amount of information about a behavioural element of the system that is of interest (such as a use-case), it extracts a trail of the methods (and method invocations) through the system that are needed in order to achieve an understanding of the implementation of the element of interest. We demonstrate the feasibility of our approach by implementing it as part of a code extraction tool, presenting a case study and evaluating the approach and tool against a set of established criteria for program comprehension tools

Amorphous slicing of extended finite state machines

Slicing is useful for many Software Engineering applications and has been widely studied for three decades, but there has been comparatively little work on slicing Extended Finite State Machines (EFSMs). This paper introduces a set of dependency based EFSM slicing algorithms and an accompanying tool. We demonstrate that our algorithms are suitable for dependence based slicing. We use our tool to conduct experiments on ten EFSMs, including benchmarks and industrial EFSMs. Ours is the first empirical study of dependence based program slicing for EFSMs. Compared to the only previously published dependence based algorithm, our average slice is smaller 40% of the time and larger only 10% of the time, with an average slice size of 35% for termination insensitive slicing