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The Substrate VM Project

Substrate VM is an internal project name for the technology behind GraalVM Native Image. This guide shows how to set up a development environment for the project.

To get started, install mx. Then point the JAVA_HOME variable to a JDK that supports a compatible version of the JVM Compiler Interface (JVMCI). JVMCI is a privileged, low-level interface to the JVM that can read metadata from the VM, such as method bytecode, and install machine code into the VM. Obtain JVMCI-enabled:

Prerequisites

For compilation, native-image depends on the local toolchain. Install glibc-devel, zlib-devel (header files for the C library and zlib) and gcc, using a package manager available on your OS. Some Linux distributions may additionally require libstdc++-static.

Building native images on Windows requires a Microsoft Visual C++ (MSVC) that comes with Visual Studio 2017 15.5.5 or later. In addition, a proper Developer Command Prompt for your version of Visual Studio. On Windows, the native-image tool only works when it is executed from the x64 Native Tools Command Prompt.

cd substratevm
mx build

echo "public class HelloWorld { public static void main(String[] args) { System.out.println(\"Hello World\"); } }" > HelloWorld.java
$JAVA_HOME/bin/javac HelloWorld.java
mx native-image HelloWorld
./helloworld

To build polyglot images, refer to the documentation in the VM suite.

Build Script

Using Native Image in a development environment requires the mx tool to be installed first, so that it is on your PATH. Visit the MX Homepage for more details.

In the main directory, invoke mx help to see the list of commands. Most of the commands are inherited from the Graal and Truffle code bases. More information on a specific command is available by running mx help <command>. The most important commands are:

  • build: compile all Java and native code
  • clean: remove all compilation artifacts
  • ideinit: create project files for Eclipse and other common IDEs See the documentation on IDE integration for details.

Building images

After running mx build you can use mx native-image to build native images. You can specify the main entry point, i.e., the application you want to create the image for. For more information run mx native-image --help.

A native image generation is performed by a Java program, a Native Image builder, that runs on a JVMCI-enabled JDK. You can debug it with a regular Java debugger. Use mx native-image --debug-attach to start native image generation so that it waits for a Java debugger to attach first (by default, at port 8000). In Eclipse, use the debugging configuration substratevm-localhost-8000 to attach to it. This debugging configuration is automatically generated by mx ideinit.

If you have to debug the compiler graphs that are built as part of an image, proceed to the debugging page. You can use the Ideal Graph Visualizer (IGV) tool to view individual compilation steps:

mx igv &>/dev/null &
mx native-image HelloWorld -H:Dump= -H:MethodFilter=HelloWorld.*

Options

More information about options and the important distinction between hosted and runtime options is available here.

Project Structure

The list of projects is defined in a custom format in the file mx.substratevm/suite.py. It is never necessary to create new projects in the IDE. Instead, a new project is created by adding it in suite.py and running mx ideinit to generate a corresponding IDE project.

Code Formatting

Style rules and procedures for checking adherence are described in the style guide.

Troubleshooting Eclipse

Sometimes, Eclipse gives strange error messages, especially after pulling a bigger changeset. Also, projects are frequently added or removed, leading to error messages about missing projects if you do not import new projects. The following should reset everything:

  • Delete all projects in Eclipse
  • mx clean
  • mx ideclean
  • mx fsckprojects
  • mx build
  • mx ideinit
  • Import all projects into Eclipse again

Usage Documentation

The documentation on how to use Native Image is available here or on the website.

License

The Substrate VM project is licensed under the GPL 2 with Classpath Exception.