Set Of Memory Locations Research Articles

Access-Based Localization for Octagons

Access-based localization is a two-step process. First, the set of abstract memory locations that are accessed in a procedure are determined. Then, in a subsequent fixed point iteration, the input to the respective procedure is reduced to those variables that are indeed accessed, thereby saving time and memory. The topic of this paper is access-based localization for the octagon abstract domain. For the frequently occurring scenario that only one out of two variables in some octagonal constraint is contained in the access-set of a procedure, there is a variety of opportunities how localization could be implemented. This paper presents three different approaches on how to deal with such constraints. Albeit applied to a subset of the abstract state space, two of these approaches preserve precision, i.e., the abstract state space is as precise as in the case that no localization is performed.

Functional dependencies of C functions via weakest pre-conditions

We present functional dependencies, a convenient, formal, but high-level, specification format for a piece of procedural software (function). Functional dependencies specify the set of memory locations, which may be modified by the function, and for each modified location, the set of memory locations that influence its final value. Verifying that a function respects pre-defined functional dependencies can be tricky: the embedded world uses C and Ada, which have arrays and pointers. Existing systems we know of that manipulate functional dependencies, Caveat and SPARK, are restricted to pointer-free subsets of these languages. This article deals with the functional dependencies in a programming language with full aliasing. We show how to use a weakest pre-condition calculus to generate a verification condition for pre-existing functional dependencies requirements. This verification condition can then be checked using automated theorem provers or proof assistants. With our approach, it is possible to verify the specification as it was written beforehand. We assume little about the implementation of the verification condition generator itself. Our study takes place inside the C analysis framework Frama-C, where an experimental implementation of the technique described here has been implemented on top of the WP plug-in in the development version of the tool.

A combination framework for tracking partition sizes

We describe an abstract interpretation based framework for proving relationships between sizes of memory partitions. Instances of this framework can prove traditional properties such as memory safety and program termination but can also establish upper bounds on usage of dynamically allocated memory. Our framework also stands out in its ability to prove properties of programs manipulating both heap and arrays which is considered a difficult task. Technically, we define an abstract domain that is parameterized by an abstract domain for tracking memory partitions (sets of memory locations) and by a numerical abstract domain for tracking relationships between cardinalities of the partitions. We describe algorithms to construct the transfer functions for the abstract domain in terms of the corresponding transfer functions of the parameterized abstract domains. A prototype of the framework was implemented and used to prove interesting properties of realistic programs, including programs that could not have been automatically analyzed before.

Book review: The Implementation of Prolog By Patrice Boizumault Translated from the original French by Ara M. Djamboulian and Jamal Fattouh (Princeton University Press, 1993)

As a programming language, Prolog was designed to reflect conceptual problem-solving methods rather than the architecture of any particular computer; it encourages the programmer to solve problems by describing facts and relationships, instead of trying to fit the problem into a set of memory locations and machine operations on a computer. Prolog is thus, by design, a step farther from the machine than most conventional imperative programming languages.

Computer-Based Teaching Machines

Computer-Based Teaching Machines