Developing a Generic Debugger for Advanced-Dispatching Languages

Programming-language research has introduced a considerable number of advanced-dispatching mechanisms in order to improve modularity. Advanced-dispatching mechanisms allow changing the behavior of a function without modifying their call sites and thus make the local behavior of code less comprehensible. Debuggers are tools, thus needed, which can help a developer to comprehend program behavior but current debuggers do not provide inspection of advanced-\ud dispatching-related language constructs. In this paper, we present a debugger which extends a traditional Java debugger with the ability of debugging an advanced-dispatching language constructs and a user interface for inspecting this

A graphical tool for observing state and behavioral changes at join points

To comprehend programs or to fix a bug, programmers always mentally simulate the program execution by reading the source code. Aspect-oriented programming (AOP) increases this mental effort, because it can alter the state and the behavior of the base program at a join point to any extent by executing advices. Advices are implicitly invoked in the source code and their compositions at a join point may vary according to the runtime context. They can access and even change the context values of join points. Without appropriate tools, it is difficult to notice the effects of the implicitly executed advices. The goal of my work is to increase the comprehensibility of AO programs by using a graphical tool, that can succinctly visualize the state and behavioral changes at join points

A Pointcut Language for Setting Advanced Breakpoints

In interactive debugging, it is an essential task to set breakpoints specifying where a program should be suspended at runtime to allow interaction. A debugging session may use multiple logically related breakpoints so that the sequence of their (de)activations leads to the expected suspension with the least irrelevant suspensions. A (de)activation is sometimes decided by some runtime context values related to that breakpoint. However, existing breakpoints, which are mainly based on line locations, are not expressive enough to describe the logic and the collaboration. Programmers have to manually perform some repeated tasks, thus debugging efficiency is decreased. In this paper, we identify five frequently encountered debugging scenarios that require to use multiple breakpoints. For such scenarios, it is often easier than using the traditional debugger to write pointcuts in an aspect-oriented language, and to suspend the execution at the selected join points. However, existing languages cannot handle the scenarios neatly and uniformly. Therefore, we design and implement a breakpoint language that uses pointcuts to select suspension times in the program. Our language allows programmers to use comprehensible source-level abstractions to define breakpoints. Also, multiple breakpoints can be freely composed to express their collaboration. In this way, an expected suspension can be expressively programmed and reached with less or even no irrelevant suspensions

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

Defusing the Debugging Scandal - Dedicated Debugging Technologies for Advanced Dispatching Languages

To increase program modularity, new programming paradigms, such as aspect-oriented programming, context-oriented programming, and predicated dispatching, have been researched in recent years. The new-paradigm languages allow changing behavior according to various kinds of contexts at the call sites. A recent statistics shows that at least 66\% of skilled engineers world-wide, courses and third party vendors are using languages that support AOP features. Many well-known companies are using these languages in product developments. In our research, we classified these new languages as advanced-dispatching languages. Advanced-dispatching languages are usually implemented as an extension of main-stream languages. After compilation, their programs are transformed to the compiled form of the main-stream language. Due to this compilation mechanism, the information, especially features that are specific to the advanced-dispatching languages, existing in the source code cannot be fully restored during debugging. The information loss increases the effort of comprehending advanced-dispatching programs and fixing advanced-dispatching-specific defects. In this thesis, we performed four works to improve the comprehensibility of debugging information from three debugging techniques --- interactive debugging, trace-based debugging, and slicing. We first performed research on the most common debugging technique---interactive debugging. Due to the availability of existing fault models, we proposed a generalized fault model based on four aspect-oriented-specific fault models. The generalized fault model consists of seven fault types and we found a likely pattern for fixing a defect corresponding to each type. Then, we analysed the pattern description and extracted eleven atomic advanced-dispatching-specific debugging tasks. To support the tasks, we modified an existing compiler to keep aspect-oriented information after the compilation, built a dedicated advanced dispatching debugging model, and implemented graphical user interfaces. In addition to the form of debugging information, we analysed the problem where and when the program should be suspended. In interactive debugging, breakpoints are essential to determine the suspending places. For fixing a specific defect, breakpoints are logically related. However, existing debuggers do not support to build logic between breakpoints. Therefore, programmers have to manually perform some repeated tasks. In this thesis, we analysed five common debugging scenarios that require multiple breakpoints. Targeting the investigated scenarios, we designed and implemented a breakpoint language that uses pointcuts to select suspension times in the program. In our language, an expected suspension can be expressively programmed and reached with less or even no irrelevant suspensions. Though the interactive debugging is the most commonly used debugging technique, it becomes handicapped in cases that the observed failure is far away from the defect. Locating the defect is typically a backtracking process through the execution history. However, interactive debugging is performed along with the program execution and cannot restore a past state. Trace-based debugger records events at runtime and supports inspection offline. Existing researches on trace-based debugging for advanced-dispatching languages are limited. We proposed a dedicated trace-based debugger with an user interface that allow programmers to navigate and query the recorded trace. Automation is what software aims for. Slicing is a debugging technique which automatically selects program statements that can influence the failure. It is performed on dependency graphs that contain the inter-relationships between program statements, such as control dependencies, call dependencies. We discussed how three aspect-oriented-specific constructs, which are join point shadows, program compositions, and non-argument context values, can influence the execution of aspect-oriented programs. Considering the three constructs, we developed dependency graphs that are dedicated to aspect-oriented programs, as well as a slicing algorithm that is performed on the developed dependency graphs. We showed that our approach can be applied efficiently for small projects and is able to select all relevant source code. The three debugging techniques analysed in this thesis fully cover phases before, during and after the program execution. For each technique, we have provided a debugging model that explicitly models advanced-dispatching concepts. The generated debugging information is in terms of advanced-dispatching abstractions. Thus, the comprehensibility of debugging advanced-dispatching programs is increased

A fine-grained, customizable debugger for aspect-oriented programming

To increase modularity, many aspect-oriented programming languages provide a mechanism based on implicit invocation: An aspect can influence runtime behavior of other modules without the need that these modules refer to the aspect. Recent studies show that a significant part of reported bugs in aspect-oriented programs are caused exactly by this implicitness. These bugs are difficult to detect, because aspect- oriented source code elements and their locations are transformed or even lost after compilation. We investigate four dedicated fault models and identify 11 tasks that a debugger should be able to perform for detecting aspect-orientation-specific faults. We show that existing debuggers are not powerful enough to support all identified tasks, because the aspect- oriented abstractions are lost after compilation. This paper describes the design and implementation of a debugger for aspect-oriented languages using a dedicated intermediate represen- tation preserving the abstraction level of aspect-oriented source code. This is based on a model of the more general formalism of advanced dispatching. Based on this model, we implement a user interface with functionalities supporting the identified tasks, such as visualizing point- cut evaluation and program composition. Due to the generality of our intermediate representation, our debugger can be used for a wide range of programming languages. To account for the syntactic differences among these languages, we allow language designers to customize the textual representations on the user interface

A fine-grained debugger for aspect-oriented programming

To increase modularity, aspect-oriented programming provides a mechanism based on implicit invocation: An aspect can influence runtime behavior of other modules without the need that these modules refer to the aspect. Recent studies show that a significant part of reported bugs in aspect-oriented programs are caused exactly by this implicitness. These bugs are difficult to detect because aspect-oriented source code elements and their locations are transformed or even lost after compilation. We investigate four dedicated fault models and identify ten tasks that a debugger should be able to perform for detecting aspect-orientation-specific faults. We show that existing debuggers are not powerful enough to support all identified tasks because the aspect-oriented abstractions are lost after compilation. This paper describes the design and implementation of a debugger for aspect-oriented languages using a dedicated intermediate representation preserving the abstraction level of aspect-oriented source code. We define a debugging model which is aware of aspect-oriented concepts. Based on the model, we implement a user interface with functionalities supporting the identified tasks, like visualizing pointcut evaluation and program composition

The potential of omniscient debugging for aspect-oriented programming languages

Aspect-oriented programming improve program modularity and meanwhile decreases program comprehensibility, because it can alter the program behavior implicitly. Sometimes, the implicit behavior even varies in different runtime context. To fix bugs related to aspect-oriented entities, programmers need to fully comprehend their actual behavior before taking treatments. However, in some commonly encountered debugging scenarios, existing tools fall short in providing desired information. In this paper, we have described two AO-specific debugging scenarios that require to use the program execution history. We discuss our design ideas, which are (1) a model defining AO-specific events and (2) a visualization consisting of three states, which shows different levels of details