Practical Program Restructuring for Software Evolution

这个项目正在开发和评价大型系统的工具辅助重组的新技术。软件发展的过度成本在很大程度上是由于系统的不适当结构造成的，相对于所发生的变化。工具辅助程序重构是为了以比手工更改更低的成本和风险更改系统结构而研究的。在这种方法中，工具用户选择将转换应用于所选的程序组件。该工具检查以确保每个转换将保留程序的功能行为。如果是，它将执行对所选组件的转换，并更新任何相关组件以保持一致性。工具辅助结构调整尚未证明在工业规模应用中是实际可行的。例如，一些工具需要详尽的过程间数据流分析，但在大型程序上执行成本很高。以前的重构研究没有解决常见的复杂结构，如指针算术、函数指针、注释、文本宏和条件编译。为了使大型程序的重组变得可行，这个项目正在开发和适应技术来解决这些问题。研究需求驱动的数据流是为了克服穷举数据流分析的许多性能问题。研究了查询优先级和应答缓存，以最大限度地减少繁琐和潜在的错误用户查询。测试和语义区分也可以提供重构后的正确性检查。个案研究的目的是评价所发展的技术和大规模改组的好处。

This project is developing and evaluating new techniques for tool-assisted restructuring of large systems. The excessive cost of software evolution is due in large part to inappropriate structure of a system, relative to the changes taking place. Tool-assisted program restructuring is studied for changing a system's structure at lower cost and risk than making changes by hand. In this approach, a tool user selects transformations to apply to chosen program components. The tool checks to make sure that each transformation will preserve the functional behavior of the program. If so, it performs the transformation to the chosen component and updates any related components to preserve consistency. Tool-assisted restructuring has not been demonstrated to be practical in industrial-scale applications. For example, exhaustive interprocedural data flow analysis is required by some tools, but is costly to perform on large programs. Previous restructuring research has not addressed common complicating constructs such as pointer arithmetic, function pointers, comments, textual macros, and conditional compilation. To make the restructuring of large programs practical, this project is developing and adapting techniques to address these problems. Demand-driven data flow is being investigated to overcome many performance problems of exhaustive data flow analysis. Query prioritization and caching of replies are studied to minimize burdensome and potentially incorrect user queries. Testing and semantic differencing may also provide checks of correctness after restructuring. A case study is intended to evaluate the techniques developed and the benefits of large-scale restructuring.