Ubuntu Wiki

• Launchpad Entry: https://launchpad.net/distros/ubuntu/+spec/native-java-gcj

• Created: 20051105 by MatthiasKlose

• Contributors:

• Packages affected: all packages containing java code

Summary

For each package containing java code, provide a corresponding -gcj package with java compiled to native code.

Rationale

Faster execution compared to the gij-interpreted java code. Tradeoff is higher memory consumption.

Design

Each jar file in a package installed into /usr/share/java has a corresponding file /usr/lib/gcj-4.0/ holding the corresponding so file containing the natively compiled java code. The jar file is built using the default java compiler using the arguments -O2 -fjni -findirect-dispatch.

gij is capable of working in both an interpreted mode and a compiled mode. In order to work with compiled packages, we will provide an extra package for each Java application and library that ends in -gcj which contains the compiled binaries.

To workaround limits on the number of class files and size of the byte-code, the compilation is done using the aot-compile-deb script.

The debugging symbols are provided in a corresponding -gcjdbg package.

Implementation

1. Update aot-compile-deb to compile the class/jar files in the temporary installation directories and install the results in the -gcj package(s).

2. Write a helper script for aot-compile-deb and gcj-dbtool calls. This helper script may be debhelper-based, cdbs based, or completely independant of both.

3. We will provide an example implementation for one package.

Steps to follow:

• add the two packages to the control file.
• call aot-compile-deb from the deb file.
• add gcj-dbtool calls to the postinst and preinst files.
• strip the symbols and put the symbols into the -gcjdbg package.

4. Coordinate community/developer support around updating all other Java packages (about 150 in main and universe)