Debugging Scandal: The Next Generation

In 1997, the general lack of debugging tools was termed "the debugging scandal". Today, as new languages are emerging to support software evolution, once more debugging support is lagging. The powerful abstractions offered by new languages are compiled away and transformed into complex synthetic structures. Current debugging tools only allow inspection in terms of this complex synthetic structure; they do not support observation of program executions in terms of the original development abstractions. In this position paper, we outline this problem and present two emerging lines of research that ease the burden for debugger implementers and enable developers to debug in terms of development abstractions. For both approaches we identify language-independent debugger components and those that must be implemented for every new language. One approach restores the abstractions by a tool external to the program. The other maintains the abstractions by using a dedicated execution environment, supporting the relevant abstractions. Both approaches have the potential of improving debugging support for new languages. We discuss the advantages and disadvantages of both approaches, outline a combination thereof and also discuss open challenges

Uncovering Bugs in Distributed Storage Systems during Testing (not in Production!)

Testing distributed systems is challenging due to multiple sources of nondeterminism. Conventional testing techniques, such as unit, integration and stress testing, are ineffective in preventing serious but subtle bugs from reaching production. Formal techniques, such as TLA+, can only verify high-level specifications of systems at the level of logic-based models, and fall short of checking the actual executable code. In this paper, we present a new methodology for testing distributed systems. Our approach applies advanced systematic testing techniques to thoroughly check that the executable code adheres to its high-level specifications, which significantly improves coverage of important system behaviors. Our methodology has been applied to three distributed storage systems in the Microsoft Azure cloud computing platform. In the process, numerous bugs were identified, reproduced, confirmed and fixed. These bugs required a subtle combination of concurrency and failures, making them extremely difficult to find with conventional testing techniques. An important advantage of our approach is that a bug is uncovered in a small setting and witnessed by a full system trace, which dramatically increases the productivity of debugging

The C Object System: Using C as a High-Level Object-Oriented Language

The C Object System (Cos) is a small C library which implements high-level concepts available in Clos, Objc and other object-oriented programming languages: uniform object model (class, meta-class and property-metaclass), generic functions, multi-methods, delegation, properties, exceptions, contracts and closures. Cos relies on the programmable capabilities of the C programming language to extend its syntax and to implement the aforementioned concepts as first-class objects. Cos aims at satisfying several general principles like simplicity, extensibility, reusability, efficiency and portability which are rarely met in a single programming language. Its design is tuned to provide efficient and portable implementation of message multi-dispatch and message multi-forwarding which are the heart of code extensibility and reusability. With COS features in hand, software should become as flexible and extensible as with scripting languages and as efficient and portable as expected with C programming. Likewise, Cos concepts should significantly simplify adaptive and aspect-oriented programming as well as distributed and service-oriented computingComment: 18

Sindarin: A Versatile Scripting API for the Pharo Debugger

International audienceDebugging is one of the most important and time consuming activities in software maintenance, yet mainstream debuggers are not well-adapted to several debugging scenarios. This has led to the research of new techniques covering specific families of complex bugs. Notably, recent research proposes to empower developers with scripting DSLs, plugin-based and moldable debuggers. However, these solutions are tailored to specific use-cases, or too costly for one-time-use scenarios. In this paper we argue that exposing a debugging scripting interface in mainstream debuggers helps in solving many challenging debugging scenarios. For this purpose, we present Sindarin, a scripting API that eases the expression and automation of different strategies developers pursue during their debugging sessions. Sindarin provides a GDB-like API, augmented with AST-bytecode-source code mappings and object-centric capabilities. To demonstrate the versatility of Sindarin, we reproduce several advanced breakpoints and non-trivial debugging mechanisms from the literature

Debugging statecharts models via model-code tracebility

Master'sMASTER OF SCIENC

Doctor of Philosophy

dissertationDomain-specific languages (DSLs) are increasingly popular, and there are a variety of ways to create a DSL. A DSL designer might write an interpreter from scratch, compile the DSL to another language, express DSL concepts using only the existing forms of an existing language, or implement DSL constructs using a language's extension capabilities, including macros. While extensible languages can offer the easiest opportunity for creating a DSL that takes advantage of the language's existing infrastructure, existing tools for debugging fail to adequately adapt the debugging experience to a given domain. This dissertation addresses the problem of debugging DSLs defined with macros and describes an event-oriented approach that works well with a macro-expansion view of language implementation. It pairs the mapping of DSL terms to host terms with an event mapping to convert primitive events back to domain-specific concepts. Domain-specific events can be further inspected or manipulated to construct domain-specific debuggers. This dissertation presents a core model of evaluation and events and also presents a language design-analogous to pattern-based notations for macros, but in the other direction-for describing how events in a DSL's expansion are mapped to events at the DSL's level. The domain-specific events can enable useful, domain-specific debuggers, and the dissertation introduces a design for a debugging framework to help with debugger construction. To validate the design of the debugging framework, a debugging framework, Ripple, is implemented, and this dissertation demonstrates that with a modest amount of work, Ripple can support building domain-specific debuggers

Intelligent Simulation Modeling of a Flexible Manufacturing System with Automated Guided Vehicles

Although simulation is a very flexible and cost effective problem solving technique, it has been traditionally limited to building models which are merely descriptive of the system under study. Relatively new approaches combine improvement heuristics and artificial intelligence with simulation to provide prescriptive power in simulation modeling. This study demonstrates the synergy obtained by bringing together the "learning automata theory" and simulation analysis. Intelligent objects are embedded in the simulation model of a Flexible Manufacturing System (FMS), in which Automated Guided Vehicles (AGVs) serve as the material handling system between four unique workcenters. The objective of the study is to find satisfactory AGV routing patterns along available paths to minimize the mean time spent by different kinds of parts in the system. System parameters such as different part routing and processing time requirements, arrivals distribution, number of palettes, available paths between workcenters, number and speed of AGVs can be defined by the user. The network of learning automata acts as the decision maker driving the simulation, and the FMS model acts as the training environment for the automata network; providing realistic, yet cost-effective and risk-free feedback. Object oriented design and implementation of the simulation model with a process oriented world view, graphical animation and visually interactive simulation (using GUI objects such as windows, menus, dialog boxes; mouse sensitive dynamic automaton trace charts and dynamic graphical statistical monitoring) are other issues dealt with in the study

First-class Compositions - Defining and composing object and aspect compositions with first-class operators

A considerable amount of research, especially within the OO and AOSD communities, has focused on understanding the potential and limitations of various composition techniques. This has led to a large number of proposals for alternative composition techniques, including many variations of message dispatch, inheritance, and aspect mechanisms. This paper makes the case that there is no single perfect composition technique that suits every situation, since different techniques incur different trade-offs. The proper composition technique to use depends on the particular design problem and its requirements (e.g., with respect to adaptability, reusability, understandability, robustness, etc. of the various elements of the design). However, most programming languages limit the available composition techniques to a very few. To address this, we propose a novel composition model, called Co-op. The model provides dedicated abstractions that can be used to express a wide variety of object composition techniques ("composition operators''). Examples include various forms of inheritance, delegation, and aspects. The proposed model unifies objects (with encapsulated state and a message interface) and composition operators; composition operators are specified as first-class citizens. Multiple composition operators can be combined within the same application, and composition operators can even be used to compose new composition operators from existing ones. This opens new possibilities for developing domain-specific composition operators, taxonomies of composition operators, and for reuse and refinement of composition operators. To validate and experiment with the proposed model, we have designed and implemented a simple language, Co-op/I, that we also use in this paper to show concrete examples