Table of Contents

Introduction to SimpleLanguage

We have found that the easiest way to get started with implementing your own language is by extending an existing language such as SimpleLanguage. SimpleLanguage is a demonstration language built using the Language API. The SimpleLanguage project provides a showcase on how to use the Language APIs for writing your own language. It aims to use most of the available Truffle language implementation framework (henceforth “Truffle”) features, and documents their use extensively with inline source documentation.

To start, ensure Maven3 and GraalVM are available in your system.

  1. Clone the SimpleLanguage repository using:
    git clone
  2. Set the JAVA_HOME and PATH environment variables to the GraalVM home and bin folders using a command-line shell for Linux:
    export JAVA_HOME=/path/to/graalvm
    export PATH=/path/to/graalvm/bin:$PATH

    For macOS, use:

    export JAVA_HOME=/path/to/graalvm/Contents/Home
    export PATH=/path/to/graalvm/Contents/Home/bin:$PATH
  3. Execute mvn package from the SimpleLanguage folder to build the language. The command also builds a slnative executable in the simplelanguage/native directory and a sl-component.jar language component which later can be installed into GraalVM using the GraalVM Updater tool. Please verify ithat the native-image plugin is available in your GraalVM distribution to avoid build failure:
    gu list
    gu install native-image

    You can disable the SimpleLanguage native executable build during the packaging phase by running:

    export SL_BUILD_NATIVE=false
    mvn package
  4. Run in the SimpleLanguage root folder:
    ./sl ./language/tests/

The SimpleLanguage demonstration language is licensed under the Universal Permissive License (UPL).

IDE Setup

The Truffle framework provides language-agnostic infrastructure to realize standard IDE features by providing additional APIs. If you would like to experiment with your language and get the benefits of an IDE, consider importing SimpleLanguage as an example.


The SimpleLanguage teaching project has been tested with Eclipse Neon.2 Release 4.6.2, and Eclipse Oxygen.3A. To import the project folder to the desirable Eclipse environment:

  1. Open Eclipse with a new workspace.
  2. Install the m2e and m2e-apt plugins from the Eclipse marketplace (Help -> Eclipse Marketplace).
  3. Finally, import the SimpleLanguage project from File -> Import -> Maven -> Existing Maven Projects -> browse to the SimpleLanguage folder -> Finish.


NetBeans provides GUI support for debugging arbitrary languages. In order to upload SimpleLanguage to NetBeans interface, proceed to File -> Open Project -> select simplelanguage folder -> check Open Required Projects -> open Project.

IntelliJ IDEA

The SimpleLanguage project has been tested with IntelliJ IDEA. Open IntelliJ IDEA and, from the main menu bar, select File -> Open -> Navigate to and select the simplelanguage folder -> Press OK. All dependencies will be included automatically.

Run SimpleLanguage

To run a SimpleLanguage source file, execute:

./sl language/tests/

To see assembly code for the compiled functions, run:

./sl -disassemble language/tests/

Dump Graphs

To investigate performance issues, we recommend the Ideal Graph Visualizer (IGV) – an essential tool for any language implementer building on top of Oracle GraalVM Enterprise Edition. It is available as a separate download on the Oracle Technology Network Downloads page.

  1. Unzip the downloaded package, enter the bin directory and start IGV:
    cd idealgraphvisualizer/bin
  2. Execute the following from the SimpleLanguage root folder to dump graphs to IGV:
    ./sl -dump language/tests/


To start debugging the SimpleLanguage implementation with a Java debugger, pass the -debug option to the command-line launcher of your program:

./sl -debug language/tests/

Then attach a Java remote debugger (like Eclipse) on port 8000.

SimpleLanguage Component for GraalVM

Languages implemented with the Truffle framework can be packaged as components which later can be installed into GraalVM using the GraalVM Updater tool. Running mvn package in the SimpleLanguage folder also builds a sl-component.jar. This file is the SimpleLanguage component for GraalVM and can be installed by running:

gu -L install /path/to/sl-component.jar

SimpleLanguage Native Image

A language built with Truffle can be AOT compiled using Native Image. Running mvn package in the SimpleLanguage folder also builds a slnative executable in the native directory. This executable is the full SimpleLanguage implementation as a single native application, and has no need for GraalVM in order to execute SimpleLanguage code. Besides this, a big advantage of using the native executable when compared to running on GraalVM is the greatly faster startup time as shown bellow:

time ./sl language/tests/
== running on org.graalvm.polyglot.Engine@2db0f6b2
Hello World!

real    0m0.405s
user    0m0.660s
sys     0m0.108s

time ./native/slnative
== running on org.graalvm.polyglot.Engine@7fd046f06898
Hello World!

real    0m0.004s
user    0m0.000s
sys     0m0.000s

This snipped shows a timed execution of a “Hello World” program using the sl launcher script, which runs SimpleLanguage on GraalVM, using Native Image. We can see that when running on GraalVM the execution takes 405ms. Since our SimpleLanguage program does just one print statement, we can conclude that almost all of this time is spent starting up GraalVM and initializing the language itself. When using the native executable we see that the execution takes only 4ms, showing two orders of magnitude faster startup than running on GraalVM.

For more information on the native-image tool consider reading the reference manual.

Disable SimpleLanguage Native Image Build

Building the native executable through Maven is attached to the Maven package phase. Since the native executable build can take a bit of time, we provide the option to skip this build by setting the SL_BUILD_NATIVE environment variable to false like so:

export SL_BUILD_NATIVE=false
mvn package
[INFO] ------------------------------------------------------------------------
[INFO] Building simplelanguage-graalvm-native
[INFO] ------------------------------------------------------------------------
[INFO] --- exec-maven-plugin:1.6.0:exec (make_native) @ simplelanguage-graalvm-native ---
Skipping the native image build because SL_BUILD_NATIVE is set to false.
[INFO] ------------------------------------------------------------------------
[INFO] ------------------------------------------------------------------------

Run SimpleLanguage with the Newest Compiler 21.2.0

In the outstanding case that you need to execute SimpleLanguage with the newest version of the GraalVM compiler, please follow these instructions:

  1. Download the latest JVMCI JDK 8 and point JAVA_HOME at it:
    export JAVA_HOME=/path/to/openjdk-8u292-jvmci-21.1-b04
  2. Clone the “Graal” repository from the SimpleLanguage folder:
    cd /path/to/simplelanguage
    git clone
  3. Clone the mx repository:
    git clone
  4. Add mx to your path:
    export PATH=/path/to/mx:$PATH
  5. Navigate to the compiler folder:
    cd /path/to/graal/compiler
  6. Build the GraalVM compiler:
    mx build
  7. Run SimpleLanguage using the mx command:
    mx -v --jdk=jvmci vm -cp /path/to/simplelanguage/launcher/target/launcher-21.2.0-SNAPSHOT.jar:/path/to/simplelanguage/language/target/simplelanguage.jar  /path/to/simplelanguage/language/tests/

Run SimpleLanguage Using Command Line

Executing SimpleLanguage code is normally done with the sl script which sets up the necessary command line depending on whether JAVA_HOME points to GraalVM or another JVM installation. The following subsections describe the command line for both cases.

Run SimpleLanguage with GraalVM as JAVA_HOME

Assuming JAVA_HOME points to the GraalVM installation and that the current working directory is the simplelanguage directory, to run SimpleLanguage one should execute the following command:

$JAVA_HOME/bin/java \
    -cp launcher/target/launcher-21.2.0-SNAPSHOT.jar \
    -Dtruffle.class.path.append=language/target/simplelanguage.jar \ language/tests/

In short, we place the launcher JAR on the class path and execute its main class, but we inform GraalVM of the presence of SimpleLanguage by using the -Dtruffle.class.path.append option and providing it the path to the fat language JAR. Having the language on a separate class path ensures a strong separation between the language implementation and its embedding context (in this case, the launcher).

Disable Class Path Separation

NOTE! This should only be used during development.

For development purposes it is useful to disable the class path separation and enable having the language implementation on the application class path (for example, for testing the internals of the language).

For the GraalVM distribution based on JDK 8, you can add the -XX:-UseJVMCIClassLoader option. This disables the class path isolation, enabling the language implementation to be placed on the application class path. The command line can be as follows:

$JAVA_HOME/bin/java \
    -XX:-UseJVMCIClassLoader -Dgraalvm.locatorDisabled=true \
    -cp launcher/target/launcher-21.2.0-SNAPSHOT.jar:language/target/simplelanguage.jar \ language/tests/

For the JDK 11-based distribution of GraalVM, the -XX:-UseJVMCIClassLoader option is not valid. The Java Module System isolation is used. You can achieve the same behavior using --add-exports or --upgrade-module-path. The latter is preferable.

The Language API JAR on Maven Central exports all API packages in its module-info. Apply the --upgrade-module-path option together with -Dgraalvm.locatorDisabled=true and this JAR to export Language API packages:

-Dgraalvm.locatorDisabled=true --module-path=<yourModulePath>:${truffle.dir} --upgrade-module-path=${truffle.dir}/truffle-api.jar

A sample POM using --upgrade-module-path to export Language API packages can be found in the Simple Language POM.xml file.

Other JVM Implementations

Unlike GraalVM, which includes all the dependencies needed to run a language implemented with Truffle, other JVM implementations need additional JARs to be present on the class path. These are the Language API and GraalVM SDK JARs available from Maven Central.

Assuming JAVA_HOME points to a stock JDK installation, and that the current working directory is the simplelanguage directory and the Language API and GraalVM SDK JARs are present in that directory, one can execute SimpleLanguage with the following command:

$JAVA_HOME/bin/java \
    -cp graal-sdk-21.2.0.jar:truffle-api-21.2.0.jar:launcher/target/launcher-21.2.0-SNAPSHOT.jar:language/target/simplelanguage.jar \ language/tests/