MrSpidey is a user-friendly, i n teractive static debugger for Scheme. A static debugger supplements the standard debugger by analyzing the program and pinpointing those program operations that may cause run-time errors such as dereferencing the null pointer or applying non-functions. The program analysis of MrSpidey computes value set descriptions for each term in the program and constructs a value ow graph connecting the set descriptions. Using the set descriptions, MrSpidey can identify and highlight potentially erroneous program operations, whose cause the programmer can then explore by selectively exposing portions of the value ow graph.

Feature-oriented software designs capture many interesting notions of cross-cutting, and offer a powerful method for building product-line architectures. Each cross-cutting feature is an independent module that fundamentally yields an open system from a verification perspective. We describe desiderata for verifying such modules through model checking and find that existing work on the verification of open systems fails to address most of the concerns that arise from feature-oriented systems. We therefore provide a new methodology for verifying such systems. To validate this new methodology, we have implemented it and applied it to a suite of modules that exhibit feature interaction problems. Our model checker was able to automatically locate ten problems previously found through a laborious simulationbased effort.

Aspect-oriented programming has become an increasingly important means of expressing cross-cutting program abstractions. Despite this, aspects lack support for computeraided verification. We present a technique for verifying aspect-oriented programs (expressed as state machines). Our technique assumes that the set of pointcut designators is known statically, but that the actual advice can vary. This calls for a modular technique that does not require repeated analysis of the entire system every time a developer changes advice. We present such an analysis, addressing several subtleties that arise. We also present an important optimization for handling multiple pointcut designators. We have implemented a prototype verifier and applied it to some simple but interesting cases.

Implementing first-class continuations can pose a challenge if the target machine makes no provisions for accessing and re-installing the run-time stack. In this paper, we present a novel translation that overcomes this problem. In the first half of the paper, we introduce a theoretical model that shows how to eliminate the capture and the use of first-class continuations in the presence of a generalized stack inspection mechanism. The second half of the paper explains how to translate this model into practice in two different contexts. First, we reformulate the servlet interaction language in the PLT Web server, which heavily relies on first-class continuations. Using our technique, servlet programs can be run directly under the control of non-cooperative web servers such as Apache. Second, we show how to use our new technique to copy and reconstitute the stack on MSIL.Net using exception handlers. This establishes that Scheme's first-class continuations can exist on non-cooperative virtual machines.