Theory and practice in the construction of efficient interpreters

Various characteristics of a programming language, or of the hardware on which it is to be implemented, may make interpretation a more attractive implementation technique than compilation into machine instructions. Many interpretive techniques can be employed; this thesis is mainly concerned with an efficient and flexible technique using a form of interpretive code known as indirect threaded code (ITC). An extended example of its use is given by the Setl-s implementation of Setl, a programming language based on mathematical set theory. The ITC format, in which pointers to system routines are embedded in the code, is described and its extension to cope with polymorphic operators. The operand formats and some of the system routines are described in detail to illustrate the effect of the language design on the interpreter. Setl must be compiled into indirect threaded code and its elaborate syntax demands the use of a sophisticated parser. In Setl-s an LR(1) parser is implemented as a data structure which is interpreted in a way resembling that in which ITC is interpreted at runtime. Qualitative and quantitative aspects of the compiler, interpreter and system as a whole are discussed. The semantics of a language can be defined mathematically using denotational semantics. By setting up a suitable domain structure, it is possible to devise a semantic definition which embodies the essential features of ITC. This definition can be related, on the one hand to the standard semantics of the language, and on the other to its implementation as an ITC-based interpreter. This is done for a simple language known as X10. Finally, an indication is given of how this approach could be extended to describe Setl-s, and of the insight gained from such a description. Some possible applications of the theoretical analysis in the building of ITC-based interpreters are suggested

Foundations of Empirical Software Engineering: The Legacy of Victor R. Basili

This book captures the main scientific contributions of Victor R. Basili, who has significantly shaped the field of empirical software engineering from its very start. He was the first to claim that software engineering needed to follow the model of other physical sciences and develop an experimental paradigm. By working on this postulate, he developed concepts that today are well known and widely used, including the Goal-Question-Metric method, the Quality-Improvement paradigm, and the Experience Factory. He is one of the few software pioneers who can aver that their research results are not just scientifically acclaimed but are also used as industry standards. On the occasion of his 65th birthday, celebrated with a symposium in his honor at the International Conference on Software Engineering in St. Louis, MO, USA in May 2005, Barry Boehm, Hans Dieter Rombach, and Marvin V. Zelkowitz, each a long-time collaborator of Victor R. Basili, selected the 20 most important research papers of their friend, and arranged these according to subject field. They then invited renowned researchers to write topical introductions. The result is this commented collection of timeless cornerstones of software engineering, hitherto available only in scattered publications

Execution Profiling for Non-Strict Functional Languages

Profiling tools, which measure and display the dynamic space and time behaviour of programs, are essential for identifying execution bottlenecks. A variety of such tools exist for conventional languages, but almost none for non-strict functional languages. There is a good reason for this: lazy evaluation means that the program is executed in an order which is not immediately apparent from the source code, so it is difficult to relate dynamically-gathered statistics back to the original source. This thesis examines the difficulties of profiling lazy higher-order functional languages and develops a profiling tool which overcomes them. It relates information about both the time and space requirements of the program back to the original source expressions identified by the programmer. Considerable attention is paid to the cost semantics with two abstract cost semantics, lexical scoping and evaluation scoping, being investigated. Experience gained from the two profiling schemes led to the development of a hybrid cost semantics. All three schemes are described and compared in a single formal framework. These abstract cost semantics are mapped onto an operational semantics and an implementation based on the STG-machine is developed. The manipulation of cost centres is made precise by extending the state-transition operational semantics of the STG-machine. The profiling tool has been incorporated into the Glasgow Haskell compiler ghc. Our approach preserves the correct cost attribution of costs while allowing program optimisation to proceed largely unhindered. So far as we know ghc is the only lazy functional language compiler to support source-level time profiling. The use of the profiler has lead to significant performance improvements in the compiler itself and other large application programs

Simplifying the Analysis of C++ Programs

Based on our experience of working with different C++ front ends, this thesis identifies numerous problems that complicate the analysis of C++ programs along the entire spectrum of analysis applications. We utilize library, language, and tool extensions to address these problems and offer solutions to many of them. In particular, we present efficient, expressive and non-intrusive means of dealing with abstract syntax trees of a program, which together render the visitor design pattern obsolete. We further extend C++ with open multi-methods to deal with the broader expression problem. Finally, we offer two techniques, one based on refining the type system of a language and the other on abstract interpretation, both of which allow developers to statically ensure or verify various run-time properties of their programs without having to deal with the full language semantics or even the abstract syntax tree of a program. Together, the solutions presented in this thesis make ensuring properties of interest about C++ programs available to average language users

Proceedings of the Seventh Annual Software Engineering Workshop

The Software Engineering Laboratory, software tools, software errors and cost estimation are addressed