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A highly productive platform accelerates the production of research results. The design of a Virtual Machine (VM) written in the Java TM programming language can be simplified through exploitation of interfaces, type and memory safety, automated memory management (garbage collection), exception handling, and reflection. Moreover, modern Java IDEs offer time-saving features such as refactoring, auto-completion, and code navigation. Finally, Java annotations enable compiler extensions for low-level "systems programming" while retaining IDE compatibility. These techniques collectively make complex system software more "approachable" than has been typical in the past.The Maxine VM, a metacircular Java VM implementation, has aggressively used these features since its inception. A co-designed companion tool, the Maxine Inspector, offers integrated debugging and visualization of all aspects of the VM's runtime state. The Inspector's implementation exploits advanced Java language features, embodies intimate knowledge of the VM's design, and even reuses a significant amount of VM code directly. These characteristics make Maxine a highly approachable VM research platform and a productive basis for research and teaching.

Powerful editing systems for developing complex software documents are difficult to engineer. Besides requiring efficient incremental algorithms and complex data structures, such editors must accommodate flexible editing styles, provide a consistent, coherent, and powerful user interface, support individual variations and projectwide configurations, maintain a sharable database of information concerning the documents being edited, and integrate smoothly with the other tools in the environment.Pan is a language-based editing and browsing system that exhibits these characteristics.This paper surveys the design and engineering of Pan, paying particular attention to a number of issues that pervade the system: incremental checking and analysis, information retention in the presence of change, tolerance for errors and anomalies, and extension facilities.

Debugging support for highly optimized execution environments is notoriously difficult to implement. The Truffle/-Graal platform for implementing dynamic languages offers an opportunity to resolve the apparent trade-off between debugging and high performance.Truffle/Graal-implemented languages are expressed as abstract syntax tree (AST) interpreters. They enjoy competitive performance through platform support for type specialization, partial evaluation, and dynamic optimization/deoptimization. A prototype debugger for Ruby, implemented on this platform, demonstrates that basic debugging services can be implemented with modest effort and without significant impact on program performance. Prototyped functionality includes breakpoints, both simple and conditional, at lines and at local variable assignments.The debugger interacts with running programs by inserting additional nodes at strategic AST locations; these are semantically transparent by default, but when activated can observe and interrupt execution. By becoming in effect part of the executing program, these "wrapper" nodes are subject to full runtime optimization, and they incur zero runtime overhead when debugging actions are not activated. Conditions carry no overhead beyond evaluation of the expression, which is optimized in the same way as user code, greatly improving the prospects for capturing rarely manifested bugs. When a breakpoint interrupts program execution, the platform automatically restores the full execution state of the program (expressed as Java data structures), as if running in the unoptimized AST interpreter. This then allows full introspection of the execution data structures such as the AST and method activation frames when in the interactive debugger console.Our initial evaluation indicates that such support could be permanently enabled in production environments.