Brian A. Malloy

A metrics suite for grammar-based software

One approach to measuring and managing the complexity of software, as it evolves over time, is to exploit software metrics. Metrics have been used to estimate the complexity of the maintenance effort, to facilitate change impact analysis, and as an indicator for automatic detection of a transformation that can improve the quality of a system. However, there has been little effort directed at applying software metrics to the maintenance of grammar-based software applications, such as compilers, editors, program comprehension tools and embedded systems. In this paper, we adapt the software metrics that are commonly used to measure program complexity and apply them to the measurement of the complexity of grammar-based software applications. Since the behaviour of a grammar-based application is typically choreographed by the grammar rules, the measure of complexity that our metrics provide can guide maintainers in locating problematic areas in grammar-based applications. Copyright

Efficient construction of program dependence graphs

We present a new technique for constructing a program dependence graph that contains a programs control flow, along with the usual control and data dependence information. Our algorithm constructs a program dependence graph while the program is being parsed. For programs containing only structured transfers of control, our algorithm does not require information provided by the control flow graph or post dominator tree and therefore obviates the construction of these auxiliary graphs. For programs containing explicit transfers of control, our algorithm adjusts the partial control dependence subgraph, constructed during the parse, to incorporate exact control dependence information. There are several advantages to our approach. For many programs, our algorithm may result in substantial savings in time and memory since our construction of the program dependence graph does not require the auxiliary graph. Furthermore, since we incorporate control and data flow as well as exact control dependence information into the program dependence graph, our graph has a wide range of applicability. We have implemented our algorithm by incorporating it into the Free Software Foundations GNU C compiler; currently we are performing experiments that compare our technique with the traditional approach.

An extensible program representation for object-oriented software

An extensible representation for object-oriented programs is presented. It is based on the concept of a program dependency graph and elaborated to include both control flow and data flow information. The representation takes advantage of the basic incremental philosophy of the object-oriented approach to develop a more compact representation that is useful with practical programs. The basic approach reported here provides a static view of an object-oriented program. The approach can be expanded to provide dynamic information for tools such as interactive debuggers and other runtime tools. The outline of this extension is also presented.

Program annotation in XML: a parse-tree based approach

In this paper we describe a technique that can be used to annotate source code with syntactic tags in XML format. This is achieved by modifying the parser generator bison to emit these tags for an arbitrary LALR grammar. We also discuss an immediate application of this technique, a portable modification of the gcc compiler, that allows for XML output for C, Objective C, C++ and Java programs. While our approach is based on a representation of the parse-tree and does not have the same semantic richness as other approaches, it does have the advantage of being language independent, and thus re-usable in a number of different domains.

Decorating tokens to facilitate recognition of ambiguous language constructs

Software tools are fundamental to the comprehension, analysis, testing and debugging of application systems. A necessary first step in the development of many tools is the construction of a parser front‐end that can recognize the implementation language of the system under development. In this paper, we describe our use of token decoration to facilitate recognition of ambiguous language constructs. We apply our approach to the C++ language since its grammar is replete with ambiguous derivations such as the declaration/expression and template‐declaration/expression ambiguity. We describe our implementation of a parser front‐end for C++, keystone, and we describe our results in decorating tokens for our test suite including the examples from Clause Three of the C++ standard. We are currently exploiting the keystone front‐end to develop a taxonomy for implementation‐based class testing and to reverse‐engineer Unified Modeling Language (UML) class diagrams. Copyright

Exploiting UML dynamic object modeling for the visualization of C++ programs

In this paper we present an approach to modeling and visualizing the dynamic interactions among objects in a C++ application. We exploit UML diagrams to expressively visualize both the static and dynamic properties of the application. We make use of a class diagram and call graph of the application to select the parts of the application to be modeled, thereby reducing the number of objects and methods under consideration with a concomitant reduction in the cognitive burden on the user of our system. We use aspects to insert probes into the application to enable profiling of the interactions of objects and methods and we visualize these interactions by providing sequence and communication diagrams for the parts of the program under consideration. We complement our static selectors with dynamic selectors that enable the user to further filter objects and methods from the sequence and communication diagrams, further enhancing the cognitive economy of our system. A key feature of our approach is the provision for dynamic interaction with both the profiler and the application. Interaction with the profiler enables filtering of methods and objects. Interaction with the application enables the user to supply input to the application to provide direction and enhance comprehension or debugging.

A parameterized cost model to order classes for class-based testing of C++ applications

In this paper we present the design and implementation of a class ordering system that is driven by a parameterized cost model. The parameters to the model assign weights to the edge types that describe the relationships between the classes in the graphical representation of the program. The nodes in the graph are classes and the edges express relationships between the classes. Previous research has included three or four edge types in the graph. However, to accommodate the full complement of C++ language constructs, which include template classes and functions and nested classes, we extend the graph to include six edge types. The parameters to the cost model can be tuned to remove certain types of edges in an attempt to reduce the cost of the testing effort or to reduce the cost of breaking cycles in the graph. Our case study indicates that inclusion of inheritance edges in cycle breaking considerations may reduce the number of edge removals by a factor of two or more.

Symbol table construction and name lookup in ISO C

The authors present an object oriented model of symbol table construction and name lookup for ISO C++ using the Unified Modeling Language (UML). Our use of UML class, activity and sequence diagrams serves to explicate our model and our use of patterns such as decorator and facade increase the understandability of the model. Clause three of the ISO C++ standard describes the procedures and rules for performing name lookup; our activity and sequence diagrams serve to simulate these procedures in graphical fashion. An advantage of our approach is that our model can increase C++ understandability for those practitioners with a working UML knowledge. An important contribution of our work is that our model forms the basis for construction of a parser front-end for ISO C++. Our explication of the name lookup problem represents a necessary first step in this construction and our component approach is independent of the compiler technology utilized. Our use of the UML in describing parser driven applications demonstrates how front-end development can be integrated into an object oriented framework. Construction of an ISO C++ front-end will help to increase the collection of tools for applications that use this popular language.

Instruction scheduling for the Motorola 88110

Static instruction scheduling is an important optimization to exploit instruction level parallelism. If the scheduler has to consider resource constraints to prevent structural hazards, usually the processor timing is simulated by overlaying binary matrices representing the resource usage of instructions. This technique is rather time consuming. It is shown that the timing can be simulated by a deterministic finite automaton and the matrix operations for a simulation step are replaced by two table lookups. A prototype implementation shows that about an eighteenfold speedup of the simulation can be expected. This performance gain can be used either to speed up existing scheduling algorithms or to use more complex algorithms to improve scheduling results.<<ETX>>

Using a taxonomy tool to identify changes in OO software

In this paper, we present a taxonomy that allows the maintainer to catalog OO classes based on the characteristics of the class. The characteristics of a class include the properties of data items and methods, as well as the relationships with other classes in the application. We construct a tool to track changes across multiple releases of software applications containing hundreds of classes, providing information about each changed class. Our tool identifies class changes in terms of the characteristics exhibited by classes with the same name in different releases of an application.