Separate compilation for synchronous programs

Abstract

Esterel and other imperative synchronous languages offer a rich set of statements, which can be used to conveniently describe complex control behaviors in a concise, but yet precise way. In particular, the ability to arbitrarily nest all kinds of statements including loops, local declarations, sequential and parallel control, as well as several kinds of preemption statements leads to a powerful programming language. However, this orthogonal design imposes difficult problems for the modular or separate compilation, which has to deal with special problems like the instantaneous reincarnation of locally declared variables. This paper presents a compilation procedure allowing to separately compile modules of a synchronous language. Our approach is based on two new achievements: First, we derive the information that is required for a linker to combine already compiled modules. This information is stored in a file written in an intermediate format, which is the target of our compilation procedure and the source of the linker. Second, we describe a compilation procedure for a typical imperative synchronous language to generate this intermediate format. We have implemented the approach in the upcoming version 2.0 of our Averest system.