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Interview: Porting Open Source Java to Leopard

URL: Open Source Java 6 on Leopard

At 1:09 AM on Nov 21, 2007, Geertjan wrote:

"I'm pleased to announce the first Developer Preview Release of the open-source port of Java 6 to Mac OS X," Landon Fuller wrote in his blog , two days ago. "This release includes support for 32-bit and 64-bit Intel machines running Mac OS X Leopard (10.5)." First, some background: Landon lives in the Cole Valley neighborhood of San Francisco. During the day, he runs the Infrastructure Department at Three Rings Design, a small games company. (A pic of him can be seen on the left.)

Landon, great work, you've got an early release out for open source Java 6 on Mac OS X Leopard! What's the story here? What moved you to do this?

Landon: Thanks! Honestly, I just wanted to run some software that required 1.6. Since I've long wondered what it would take to port the FreeBSD JDK to Mac OS X, it seemed like an opportune time to try. Additionally, this is the first step towards adding Mac OS X support to OpenJDK. It's my hope to see Java 7, via OpenJDK, available for Mac OS X at the same time as Solaris, Linux, and Windows.

What have been the trickiest parts of your port so far?

Landon: Getting the bugs worked out of Hotspot has been the most difficult task, by far. I've never worked with a complex JIT before, and I've found that runtime-generated code can be a whole new world of hard. The Hotspot engineers, and people like Gary Benson (OpenJDK PowerPC port), have my utmost respect.

There are also some standard APIs on Mac OS X that are incompatible with the BSDs and Linux in both interesting and unusual ways. Leopard's DTrace support has proven invaluable in tracking down bugs quickly.

What are you most proud of?

Landon: That the JVM runs! This has been an enormous learning experience in the guts of the Java runtime.

Sound seems to be missing. What else and why?

Landon: The most obvious missing feature is a native Swing UI, which is something I think is particularly important in the long-term. For now, I'm personally well-served by X11, and I hope that a native Swing implementation can be developed incrementally on top of a stable JVM.

Since I'm completely unfamiliar with Apple's CoreAudio API, I stubbed out sound so that I could get a JVM running. I'm hoping someone who has more CoreAudio experience can implement sound support—I don't expect this to be a huge task.

Lastly—and unfortunately—PowerPC support is not available, and adding it is an enormous task. I do hope to eventually include Gary Benson's OpenJDK PowerPC work.

Other than that, I don't expect there to be any significant missing functionality.

Are you working on this on your own?

Landon: I've been working on this on my own, with the intention of providing an initial release that would be genuinely useful to external developers.

I think that this "developer preview" release meets that goal, and I hope that intrepid developers will download the release, try it out, and report bugs. If they fix the bugs, that's even better!

What specific items could new contributors work on and how should they get started?

Landon: The best approach to getting started is to clone the mercurial development repository, build the JVM, and start using it for real work. You don't need to be an x86 assembly wizard—there's plenty of need for work in C, Java, and the build system.

• Build system tasks:
  —Making sure that the JVM builds correctly in most environments.
  —Fixing dyld library paths at link time.
• C tasks:
  —CoreAudio HAE sound implementation.
  —Support for Thread.setPriority() (via mach thread priority API)
• Java tasks:
  —Run your code, see what breaks!

If you have a patch, send it along, and I'll integrate it into the central mercurial repository.

Do you have a timeline in mind?

Landon: While I am very interested in supporting Java 6 development, I find the long-term view far more captivating: I'd like to see Java 7—via OpenJDK—available on Mac OS X, and the BSDs, in concert with the Solaris, Windows, and Linux releases.

In the "who is to blame" debate in the "where is Java 6 on Mac OS X" discussion, have you formulated an opinion and would you care to share it?

Landon: Rather than blame, I believe that the clear solution is to allow the development community to maintain an open source implementation of Java for Mac OS X. If the BSD port is any indication, this is an achievable goal.

I would also love to see Apple donate their own code to the OpenJDK project.

You're making use of open source Java to port Java to Mac OS X. Do you see similar ports happening in the future or some other similar implementation?

Landon: Absolutely. The OpenJDK project has proposed the formation of the OpenJDK Porters Group, focusing on:

• Ports to new architectures
• Ports to new operating systems
• Collaboration with other OpenJDK porting projects

I hope that this is only the beginning of community contributions to OpenJDK porting efforts.