The OpenJDK Common Virtual Machine Interface (CVMI) Project

The OpenJDK CVMI project originated as part of the OpenJDK challenge with the goal of providing a common library interface for the three Free Software class libraries (Sun OpenJDK, GNU Classpath and Apache Harmony). Its initial aims are threefold:

1. Examine and document the existing VM interface used by OpenJDK
2. Compare this with the existing GNU Classpath VM interface, and look at how other VMs (e.g. CACAO, JNode) have begun the move from this to the largely undocumented OpenJDK interface
3. Experiment on the CVMI branch with a VM interface closer to the Java-based approach used by GNU Classpath

This site aims to be the focal point for these efforts. It will provide documentation of the current interface and of the changes being made on the CVMI branch, along with other issues of note. The IcedTea wiki will be used for more fluid discussion.

Topics

• The Existing OpenJDK VM Interface
  • Class Library-->VM calls
  • VM-->Class Library calls
• The Common Virtual Machine Interface; class-by-class method descriptions
• Approaches to Implementing the OpenJDK VM Interface
• Porting JamVM to the CVMI

Mercurial Repositories

• OpenJDK CVMI port; includes an alternative interface for OpenJDK using VMxxx-style Java classes and HotSpot support for these classes.
• JamVM CVMI port; includes a port of JamVM to work with the CVMI tree.

Relevant Blogs

• Comparing and Contrasting VM Interfaces; a description of the class library to VM calls in OpenJDK and GNU Classpath
• Comparing and Contrasting VM Interfaces II: From the VM to the Library; an overview of areas where the VM is implicitly expected to make class library calls
• Sharing Secrets; how implementation classes access core classes like java.lang.Object

Other Relevant Links

• A runtime overview of HotSpot