openjdk.md

OpenJDK

Open source, reference implementation. Resulted from a partial open sourcing of Oracle's Java implementation.

http://openjdk.java.net/

Sample output of java -version on Ubuntu 14.04:

java version "1.7.0_65"
OpenJDK Runtime Environment (IcedTea 2.5.3) (7u71-2.5.3-0ubuntu0.14.04.1)
OpenJDK 64-Bit Server VM (build 24.65-b04, mixed mode)

Source browser and mercurial URLs: http://hg.openjdk.java.net/. Mercurial.

Versioning

TODO how is it versioned?

It seems to use:

jdk8u60-b12

to mean:

• 8: major
• 60: minor, u for Update
• 12: patch, b for Build

TODO: jdk8u60-b26 vs jdk8-b27? AKA http://hg.openjdk.java.net/jdk8u vs http://hg.openjdk.java.net/jdk8

OpenJDK 8 source code

• https://github.com/hgomez/obuildfactory
• https://gfiber.googlesource.com/buildroot/+/master/package/openjdk-bin/openjdk-bin.mk
• https://github.com/florian-gauvin/Buildroot-Openjdk/blob/f9962b187c71678dae0fcd7913876127b0b85a7d/package/openjdk/openjdk.mk
• https://en.wikipedia.org/wiki/JamVM

Clone and build

Get sources:

hg clone http://hg.openjdk.java.net/jdk8/jdk8
cd jdk8
sh get_source.sh

The get_source.sh is needed since the source is split across many HG repositories.

The entire JDK 8 takes up 900M.

Ubuntu 14.04 build dependencies (my printer stopped working afterwards...):

sudo aptitude install libcups2-dev libfreetype6-dev libasound2-dev ccache

Build everything with:

bash configure
make -j $(nproc)

Took 25 minutes on a mid range computer from 2012.

make help teaches you more, e.g. how to build only certain parts of the JDK:

make -j $(nproc) hotspot
make -j $(nproc) jdk

Finally:

cd build/linux-x86_64-normal-server-release/jdk/bin
./java -version

Sample output:

openjdk version "1.8.0-internal"
OpenJDK Runtime Environment (build 1.8.0-internal-ciro_2015_03_10_22_39-b00)
OpenJDK 64-Bit Server VM (build 25.0-b70, mixed mode)

Source tree

Some interesting files and directories:

• jdk/src/share/classes/java: JCL

• hotspot: the VM, including many native methods. There are also some native methods under jdk/src.

  • hotspot/src/share/vm: platform agnostic VM code, mainly C++.

  • hotspot/src/share/os: OS specific code, contains bsd, linux, posix (used for all others but Windows), solaris, windows

    Contains the definition of several native methods.

  • hotspot/src/share/cpu: OS specific code

    • hotspot/src/share/cpu/zero: CPU agnostic interpreter-only implementation when speed is not important.

      Started by IcedTea.

      http://openjdk.java.net/projects/zero/

• langtools/src/share/classes/com/sun/tools/javadoc/Main.java: Javadoc

• langtools/src/share/classes/com/sun/tools/javac/Main.java: Javac

Contribution process

Issue tracker

The Java process is very closed, probably because of Oracle?

I can't even manage to post an issue, so I wonder if it is even possible to have patches merged.

Create a new issue or feature request: http://bugreport.java.com/submit_intro.do Bugs only appear after review. Bulls***.

TODO how to browse the bugs? More bull****?

TODO vs https://bugs.openjdk.java.net? On that site you need a login, and to get it you need Author status...

http://programmers.stackexchange.com/questions/216203/how-does-the-maintenance-of-openjdk-work-in-practice