Scala on Avian

This project is intended to help make Scala portable to platforms where a full-fledged JVM is difficult or impossible to install.

Status

Currently, all it does is create an executable which embeds the Avian VM and relies on a filesystem-based classpath containing the Avian, OpenJDK, and Scala classes needed to run the Scala interpreter. Future goals include:

• Use ProGuard to shrink the classpath to a minimal size. This will require configuring ProGuard to keep all the code Scala loads via reflection or similar means which ProGuard can't detect itself.

• Support loading classes from embedded JARs to allow the executable to work without any external dependencies. Currently, Scala seems to require direct access to resources in the classpath, so we'll either need to fool it into thinking it's accessing the filesystem when it's really reading from an embedded JAR, or else find out if there's another way for Scala to operate without accessing classpath resources directly.

• Support exclusively AOT-compiled operation (or AOT plus interpretation if the runtime-loaded bytecode is not performance-sensitive). This is necessary to work on platforms such as iOS, where memory cannot be made both writable and executable, and thus JIT compilation is impossible. How this is done will depend on if and how Scala does runtime bytecode generation.

• Support platforms other than Linux. This should be easy.

Building and Testing

$ make avian=<absolute path of avian source tree> \
    scala=<absolute path of scala binary distribution> \
    openjdk=<absolute path of openjdk binary distribution> \
    openjdk-src=<absolute path of openjdk source code>

$ build/scala build/stage1

Note that you may need to reset your terminal after running the above (e.g. using the "reset" command), since JLine does seem to clean up after itself when run under Avian. I haven't had a chance to investigate why that is yet.