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Native Image of the Scala Compiler

This demo demonstrates how to build a native image of the Scala compiler.

First, make sure that environment variables SCALA_HOME and GRAALVM_HOME point to Scala 2.12.x and GraalVM. Then build the sbt project scalac-substitutions:

cd scalac-substitutions
sbt package
cd ../

To build the native image of the Scala compiler run


The produced native image is called scalac and has no dependencies on the JDK.

The script scalac-native calls the generated compiler and passes all the required parameters (just like scala does).

Let's see how we compare to the JVM on the first run:

$ time $SCALA_HOME/bin/scalac HelloWorld.scala

real	0m2.315s
user	0m5.868s
sys	0m0.248s

& time ./scalac-native HelloWorld.scala

real	0m0.177s
user	0m0.129s
sys	0m0.034s

When compiled with profile-guided optimization (PGO) the native scalac is as fast as the one running on the JVM (with the C2 compiler).

Support for Macros

For macros to work the macro classes must be known to the image builder of the Scala compiler. To try a scalac image that includes macro run

./scalac-native macros/GreetingMacros.scala -d macros/

Now we can compile a project that uses macros from GreetingMacros.scala:

./scalac-native -cp macros/ HelloMacros.scala

We can run the compiled program with:

$ scala HelloMacros
Hello, World!
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