Marco: Safe, Expressive Macros for Any Language

Abstract

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.

SPL

“…Jeannie takes this to the extreme by embedding Java into C and vice versa [Hirzel and Grimm 2007]. Finally, Marco is a macro system that supports multiple target languages, including C++, while still offering early error detection [Lee et al 2012]. In contrast to these approaches, extensibility in SPL focuses on operators.…”

Pluggable Controllers and Nano-Patterns in Java with Lola

“…Macro systems do not usually differentiate between lexical elements of the hosting language such as expressions, identifiers, constants, etc. One preprocessor that differs in this aspect is the Marco preprocessor [56], which has a way to reduce the coupling between the host language to the macro system.…”

Safely Composable Type-Specific Languages

“…They provide support for generating new programming languages and tooling in a modular manner. The Marco language [16] similarly provides macro definition at a level of abstraction that is largely independent of the target language. In these approaches, each TSL is external relative to the host language; in contrast, Wyvern focuses on internal extensibility, improving interoperability and composability.…”