Ant script to recompile the JDK runtime with full debug symbols

debug_jdk.xml

<project name="create rt_debug.jar" default="makejar" basedir=".">
    <target name="init">
        <property environment="env"/>
        <property name="project.build" location="build"/>
        <property name="project.src" location="${project.build}/src"/>
        <property name="project.classes" location="${project.build}/classes"/>
        <property name="project.dist" location="${project.build}/dist"/>
        <path id="project.classpath">
            <fileset dir="${env.JAVA_HOME}/jre/lib">
                <include name="*.jar"/>
            </fileset>
        </path>
    </target>
 
    <target name="clean" depends="init">
        <delete dir="${project.build}" quiet="true"/>
        <mkdir dir="${project.build}"/>
    </target>
 
    <target name="unpack" depends="init, clean">
        <unzip src="${env.JAVA_HOME}/src.zip" dest="${project.src}"/>   
    </target>
 
    <target name="build" depends="unpack">
        <mkdir dir="${project.classes}"/>
        <javac srcdir="${project.src}" classpathref="project.classpath"
            destdir="${project.classes}" debug="on" includeAntRuntime="false"
            fork="true" memoryMaximumSize="4096m" failonerror="false">
        </javac>
    </target>
 
    <target name="makejar" depends="build">
        <mkdir dir="${project.dist}"/>
        <copy file="${env.JAVA_HOME}/jre/lib/rt.jar" tofile="${project.dist}/rt_debug.jar"/>
        <jar jarfile="${project.dist}/rt_debug.jar" update="true" compress="true">
            <fileset dir="${project.classes}"/>
        </jar>
        <echo>
            Debug library built. You can find it at ${project.dist}/rt_debug.jar. Use any of the following methods to make use of it:
            - copy it to ${env.JAVA_HOME}/jre/lib/endorsed/ (create the directory if it doesn't exists)
            - use the -Xbootclasspath property to specify this jar
            - overwrite ${env.JAVA_HOME}/jre/lib/rt.jar with it (backing up the original is highly recommended!)
        </echo>
    </target>
</project>