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Things libgcj hackers should know
If you want to hack on the libgcj files you need to be aware of the
following things. There are probably lots of other things that should be
explained in this HACKING file. Please add them if you discover them :)
If you plan to modify a .java file, you will need to configure with
--enable-java-maintainer-mode. In order to make this work properly,
you will need to have 'ecj1' and 'gjavah' executables in your PATH at
build time.
One way to do this is to download ecj.jar (see contrib/download_ecj)
and write a simple wrapper script like:
#! /bin/sh
gij -cp /home/tromey/gnu/Generics/trunk/ecj.jar \
org.eclipse.jdt.internal.compiler.batch.GCCMain \
For gjavah, you can make a from the classes in
classpath/lib/tools/ and write a gjavah script like:
#! /bin/sh
gij -cp $dir/ \ \
Another way to get a version of gjavah is to first do a
non-maintainer-mode build and use the newly installed gjavah.
To regenerate libjava/configure, first run aclocal passing the flags
found near the top of, then autoconf. H. J. Lu writes that
this can be done using these commands:
cd libjava &&
rm -f aclocal.m4 &&
ACFLAGS=$(grep "^ACLOCAL_AMFLAGS" | sed -e "s/ACLOCAL_AMFLAGS[ \t ]*=//") &&
aclocal-1.11 $ACFLAGS &&
rm -f configure &&
autoconf-2.64 &&
rm -fr autom4te.cache
See the GCC documentation which auto* versions to use.
libgcj uses GNU Classpath as an upstream provider. Snapshots of
Classpath are imported into the libgcj source tree. Some classes are
overridden by local versions; these files still appear in the libgcj
To import a new release:
- Check out a classpath snapshot or take a release tar.gz file.
I use 'cvs export' for this. Make a tag to ensure future hackers
know exactly what revision was checked out; tags are of the form
'libgcj-import-DATE' (when using a tagged checkout do:
- ./ && ./configure && make dist
to get a proper .tar.gz for importing below).
- Get a svn checkout of
this contains "pure" GNU Classpath inside the GCC tree.
- Clean it up and get the files from a new version:
- find classpath -type f | grep -v '/\.svn' | grep -v '/\.cvs' | xargs rm
- tar zxf classpath-x.tar.gz
- cp -r classpath-x/* classpath
- Add/Remove files:
- svn status classpath | grep ^\! | cut -c8- | xargs svn remove
- svn status classpath | grep ^\? | cut -c8- | xargs svn add
- If there are any empty directories now they can be removed. You can find
candidates (dirs with files removed) with:
- for i in `svn status classpath | grep ^D | cut -c8-`; \
do ls -d `dirname $i`; done | uniq
- Update vendor branch
- svn commit classpath
- Note the new revision number (Xrev)
- Get a fresh svn trunk checkout and cd gcc/libjava
- Merge the changes between classpath versions into the trunk.
svn merge -rXrev-1:Xrev \
svn+ssh:// \
- Resolve any conflicts pointed out by svn status classpath | grep ^C
- files will be regenerated in the next step.
- Other files should have a "GCJ LOCAL" comment, and/or are mentioned
in the classpath/ChangeLog.gcj file.
(Don't forget to svn resolved files.)
- Use auto* to create configure,, etc
Make sure you have Automake 1.11.1 installed. Exactly that version!
You have to make sure to use the gcc libtool.m4 and gcc lt* scripts
cd .../classpath
cp ../../lt* .
cp ../../config.sub ../../config.guess .
aclocal -I m4 -I ../.. -I ../../config
rm -rf autom4te.cache
cd ..
scripts/makemake.tcl >
- Remove the generated class and header files:
find classpath -name '*.class' | xargs -r rm -f
find gnu java javax org sun -name '*.h' \
| xargs -r grep -Fl 'DO NOT EDIT THIS FILE - it is machine generated' \
| xargs -r rm -f
- Build, fix, till everything works.
Be sure to build all peers (--enable-java-awt=gtk,xlib,qt
--enable-gconf-peer --enable-gstreamer-peer).
Be sure to build gjdoc (--enable-gjdoc).
Be sure to update gnu/classpath/ to reflect
the new version
Possibly update the gcj/javaprims.h file with scripts/
(See below, it can only be done after the first source->bytecode
pass has finished.)
You will need to configure with --enable-java-maintainer-mode and you
will need to update the .class files and generated CNI header files in
your working tree
- Add/Remove newly generated files:
- svn status classpath | grep '^!.*\.class$' | cut -c8- | xargs svn remove
- svn status classpath | grep '^?' | cut -c8- | xargs svn add
- svn status gnu java javax org sun | grep '^!.*\.h$' | cut -c8- | xargs svn remove
- svn status gnu java javax org sun | grep '^?' | cut -c8- | xargs svn add
Over time we plan to remove as many of the remaining divergences as
File additions and deletions require running scripts/makemake.tcl
before running automake.
In general you should not make any changes in the classpath/
directory. Changes here should come via imports from upstream.
However, there are three (known) exceptions to this rule:
* In an emergency, such as a bootstrap breakage, it is ok to commit a
patch provided that the problem is resolved (by fixing a compiler
bug or fixing the Classpath bug upstream) somehow and the resolution
is later checked in (erasing the local diff).
* On a release branch to fix a bug, where a full-scale import of
Classpath is not advisable.
* We maintain a fair number of divergences in the build system.
This is a pain but they don't seem suitable for upstream.
You can develop in a GCC tree using a CVS checkout of Classpath, most
of the time. (The exceptions are when an incompatible change has been
made in Classpath and some core part of libgcj has not yet been
The way to set this up is very similar to importing a new version of
Classpath into the libgcj tree. In your working tree:
* cd gcc/libjava; rm -rf classpath
* cvs co classpath
* cd classpath
Now run the auto tools as specified in the import process; then
cd ..
* Run 'scripts/makemake.tcl >' in the source tree
* Run automake for libgcj
Now you should be ready to go.
If you are working in a tree like this, you must remember to run
makemake.tcl and automake whenever you update your embedded classpath
If you add a class to java.lang,, or java.util
(including sub-packages, like java.lang.ref).
* Edit gcj/javaprims.h
* Go to the `namespace java' line, and delete that entire block (the
entire contents of the namespace)
* Then insert the output of `perl scripts/' into the file
at that point. This must be run from the source tree, in
libjava/classpath/lib; it uses the .class file name to determine
what to print.