ConSUS: a light-weight program conditioner

Abstract

Program conditioning consists of identifying and removing a set of statements which cannot be executed when a condition of interest holds at some point in a program. It has been applied to problems in maintenance, testing, re-use and re-engineering. Program conditioning relies upon both symbolic execution and reasoning about symbolic predicates. Automation of the process therefore requires some form of automated theorem proving. However, the use of a full-power 'heavyweight' theorem prover would impose unrealistic performance constraints. This paper reports on a lightweight approach to theorem proving using the FermaT simplify decision procedure. This is used as a component to ConSUS, a program conditioning system for the Wide Spectrum Language WSL. The paper describes the symbolic execution algorithm used by ConSUS, which prunes as it conditions. The paper also provides empirical evidence that conditioning produces a significant reduction in program size and, although exponential in the worst case, the conditioning system has low degree polynomial behaviour in many cases, thereby making it scalable to unit level applications of program conditioning.

Theoretical foundations of dynamic program slicing

“…These observation have led several authors to observe that conditioned slicing "subsumes" static and dynamic slicing [12,19,23]. However, this use of the term "subsumes" differs from the one used herein.…”

Specialization slicing

“…A common approach, which is used in this paper and goes back to the introduction of PDGs for program slicing [Ottenstein and Ottenstein 1984], is that no evaluation or simplification is performed, and the elements of the output slice are all elements from the input program. There has been more recent work by Snelting et al [2006], Canfora et al [1994], Fox et al [2004], Danicic et al [2005], and Jaffar et al [2012] that combines slicing-like operations with simplification operations or symbolic execution. Some of that work still uses SDG-like structures.…”

“…Conditioned slicing Fox et al 2004;Danicic et al 2005] combines static slicing and program simplification to produce executable program slices. The simplification phase propagates information forward to remove statements that cannot be executed when a given constraint holds on the initial state.…”

“…The simplification phase propagates information forward to remove statements that cannot be executed when a given constraint holds on the initial state. Some of this work merely applies off-the-shelf slicing algorithms for the static-slicing component and hence could adopt the specialization-slicing algorithm presented in this paper: Danicic et al [2005] use the static-slicing algorithm of Ouarbya et al [2002]; Fox et al [2004] use an implementation of Weiser's algorithm. Harman and Danicic [1997] studied what they call amorphous slicing, which drops the requirement of syntax preservation.…”

Using Abstraction-driven Slicing for Postmortem Analysis of Software

“…Instead, its existence in the current abstraction map would make the collection of relevant data values terminate in shorter time and with more precise results. 9], [10,10], [11,19], [20,20], [21, +∞)}.…”