1. Get a GCC snapshot or obtain GCC via CVS.

2. Make a compile directory

  $ mkdir compile

3. Move the snapshot into the compile dir, e.g.

  $ cd compile
  $ mv ../gcc-20001211.tar.gz .
  $ gunzip *.gz
  $ tar xfv *.tar
  $ ln -s gcc-20001211 gcc

4. Tell the build system you want to build libgcj

  Have a look at the toplevel configure.in (gcc/configure.in) and
  make sure that the variable `noconfigdirs' isn't assigned to
  something (like target-libjava or ${libgcj}.)


  Also, check for platform-specific assignments of `noconfigdirs' with
  ${libgcj}; if ${libgcj} is listed for your platform, remove it before
  configuring.

5. Compile and install gcc/gcj/libgcj

  $ cd compile
  $ mkdir objdir
  $ cd objdir
  $ ../gcc/configure --enable-threads=posix --prefix=/home/joerg/gcc \
    --enable-shared --enable-languages=c++,java \
    --with-as=/opt/gnu/bin/as --with-ld=/opt/gnu/bin/ld
  $ make bootstrap
  $ make
  $ make install

The Boehm GC is the collector picked up by default.

If you compile under Linux you could omit the last two options. Under
Solaris you'll need them. If you omit '--prefix' the compiled source
will be installed under /usr/local. For more information about
installing gcc and/or configuration options see:

  http://gcc.gnu.org/install/index.html

If you have a broken gas/bin-utils (such as Debian potato) then you
want to edit the auto-host.h file and remove the definition of
HAVE_GAS_HIDDEN after configuring, but before typeing make.  See
the FAQ for more information.

6. Adjust your environment

Reflect your choice of --prefix value to your environment. It depends
on which shell you're running. For csh compatible shells, edit a file
env.csh:

setenv PATH /home/joerg/gcc/bin:$PATH
setenv LD_LIBRARY_PATH /home/joerg/gcc/lib

  $ source env.csh

7. Edit a file HelloWorld.java

  public class HelloWorld {
    public static void main(String [] args) {
      System.out.println("Hello");
    }
  }

8. Compile and run HelloWorld

 $ gcj --main=HelloWorld -o HelloWorld HelloWorld.java
 $ ./HelloWorld