Abstract. A meta-program is a program that generates or manipulates another program; in homogeneous meta-programming, a program may generate new parts of, or manipulate, itself. Meta-programming has been used extensively since macros were introduced to Lisp, yet we have little idea how formally to reason about metaprograms. This paper provides the first program logics for homogeneous metaprogramming – using a variant of MiniML □ e by Davies and Pfenning as underlying meta-programming language. We show the applicability of our approach by reasoning about example meta-programs from the literature. We also demonstrate that our logics are relatively complete in the sense of Cook, enable the inductive derivation of characteristic formulae, and exactly capture the observational properties induced by the operational semantics. 1

This study proposes a new framework that can effectively apply unit testing to concurrent programs, which are difficult to develop and debug. Test-driven development, a practice enabling developers to detect bugs early by incorporating unit testing into the development process, has become wide-spread, but it has only been effective for programs with a single thread of control. The order of operations in different threads is essentially non-deterministic, making it more complicated to reason about program properties in concurrent programs than in single-threaded programs. Because hardware, operating systems, and compiler optimizations influence the order in which operations in different threads are executed, debugging is problematic since a problem often cannot be reproduced on other machines. Multicore processors, which have replaced older single-core designs, have exacerbated these problems because they demand the use of concurrency if programs are to benefit from new processors. The existing tools for unit testing programs are either flawed or too costly.

Code generation is the leading approach to making high-performance software reusable. Effects are indispensable in code generators, whether to report failures or to insert let-statements and ifguards. Extensive painful experience shows that unrestricted effects interact with generated binders in undesirable ways to produce unexpectedly unbound variables, or worse, unexpectedly bound ones. These subtleties prevent experts in the application domain, not in programming languages, from using and extending the generator. A pressing problem is thus to express the desired effects while regulating them so that the generated code is correct, or at least correctly scoped, by construction. In an imminently practical code-generation framework, we show how to express arbitrary effects, including mutable references and delimited control, that move open code across generated binders. The static types of our generator expressions not only ensure that a well-typed generator produces well-typed and well-scoped code, but also express the lexical scopes of generated binders and prevent mixing up variables with different scopes. This precise notion of lexical scope subsumes the complaints about intuitively wrong example generators in the literature. For the first time, we demonstrate statically safe let-insertion across an arbitrary number of binders. Our framework is implemented as a Haskell library that embeds an extensible typed higher-order domain-specific language. It may be regarded as ‘staged Haskell. ’ The library is convenient to use thanks to the maturity of Haskell, higher-order abstract syntax, and polymorphism over generated type environments.

Abstract. Macros improve expressiveness, concision, abstraction, and language interoperability without changing the programming language itself. They are indispensable for building increasingly prevalent multilingual applications. Unfortunately, existing macro systems are wellencapsulated but unsafe (e.g., the C preprocessor) or are safe but tightlyintegrated with the language implementation (e.g., Scheme macros). This paper introduces Marco, the first macro system that seeks both encapsulation and safety. Marco is based on the observation that the macro system need not know all the syntactic and semantic rules of the target language but must only directly enforce some rules, such as variable name binding. Using this observation, Marco off-loads most rule checking to unmodified target-language compilers and interpreters and thus becomes language-scalable. We describe the Marco language, its languageindependent safety analysis, and how it uses two example target-language analysis plug-ins, one for C++ and one for SQL. This approach opens the door to safe and expressive macros for any language. 1