libjava/HACKING

   1 Things libgcj hackers should know
   2 ---------------------------------
   3
   4 If you want to hack on the libgcj files you need to be aware of the
   5 following things. There are probably lots of other things that should be
   6 explained in this HACKING file. Please add them if you discover them :)
   7
   8 --
   9
  10 If you plan to modify a .java file, you will need to configure with
  11 --enable-java-maintainer-mode.  In order to make this work properly,
  12 you will need to have 'ecj1' and 'gjavah' executables in your PATH at
  13 build time.
  14
  15 One way to do this is to download ecj.jar (see contrib/download_ecj)
  16 and write a simple wrapper script like:
  17
  18     #! /bin/sh
  19     gij -cp /home/tromey/gnu/Generics/trunk/ecj.jar \
  20        org.eclipse.jdt.internal.compiler.batch.GCCMain \
  21        ${1+"$@"}
  22
  23 For gjavah, you can make a tools.zip from the classes in
  24 classpath/lib/tools/ and write a gjavah script like:
  25
  26     #! /bin/sh
  27     dir=/home/tromey/gnu/Generics/Gcjh
  28     gij -cp $dir/tools.zip \
  29        gnu.classpath.tools.javah.Main \
  30        ${1+"$@"}
  31
  32 Another way to get a version of gjavah is to first do a
  33 non-maintainer-mode build and use the newly installed gjavah.
  34
  35 --
  36
  37 libgcj uses GNU Classpath as an upstream provider.  Snapshots of
  38 Classpath are imported into the libgcj source tree.  Some classes are
  39 overridden by local versions; these files still appear in the libgcj
  40 tree.
  41
  42 To import a new release:
  43
  44 - Check out a classpath snapshot or take a release tar.gz file.
  45   I use 'cvs export' for this.  Make a tag to ensure future hackers
  46   know exactly what revision was checked out; tags are of the form
  47   'libgcj-import-DATE' (when using a tagged checkout do:
  48   - ./autogen.sh && ./configure && make dist
  49   to get a proper .tar.gz for importing below).
  50 - Get a svn checkout of
  51   svn+ssh://gcc.gnu.org/svn/gcc/branches/CLASSPATH/libjava/classpath
  52   this contains "pure" GNU Classpath inside the GCC tree.
  53 - Clean it up and get the files from a new version:
  54   - find classpath -type f | grep -v /\.svn | grep -v /\.cvs | xargs rm
  55   - tar zxf classpath-x.tar.gz
  56   - cp -r classpath-x/* classpath
  57 - Add/Remove files:
  58   - svn status classpath | grep ^\! | cut -c8- | xargs svn remove
  59   - svn status classpath | grep ^\? | cut -c8- | xargs svn add
  60 - If there are any empty directories now they can be removed. You can find
  61   candidates (dirs with files removed) with:
  62   - for i in `svn status classpath | grep ^D | cut -c8-`; \
  63       do ls -d `dirname $i`; done | uniq
  64 - Update vendor branch
  65   - svn commit classpath
  66 - Note the new revision number (Xrev)
  67 - Get a fresh svn trunk checkout and cd gcc/libjava
  68 - Merge the changes between classpath versions into the trunk.
  69   svn merge -rXrev-1:Xrev \
  70   svn+ssh://gcc.gnu.org/svn/gcc/branches/CLASSPATH/libjava/classpath \
  71   classpath
  72 - Resolve any conflicts pointed out by svn status classpath | grep ^C
  73   - Makefile.in files will be regenerated in the next step.
  74   - Other files should have a "GCJ LOCAL" comment, and/or are mentioned
  75     in the classpath/ChangeLog.gcj file.
  76    (Don't forget to svn resolved files.)
  77 - Use auto* to create configure, Makefile.in, etc
  78   Make sure you have Automake 1.9.6 installed. Exactly that version!
  79   You have to make sure to use the gcc libtool.m4 and gcc lt* scripts
  80   cd .../classpath
  81   cp ../../lt* .
  82   cp ../../config.sub ../../config.guess .
  83   aclocal -I m4 -I ../.. -I ../../config
  84   autoconf
  85   autoheader
  86   automake
  87   rm -rf autom4te.cache
  88   cd ..
  89   scripts/makemake.tcl > sources.am
  90   automake
  91 - Build, fix, till everything works.
  92   Be sure to update gnu/classpath/Configuration.java to reflect
  93     the new version
  94   Possibly update the gcj/javaprims.h file with scripts/classes.pl
  95   (See below, it can only be done after the first source->bytecode
  96    pass has finished.)
  97   You will need to configure with --enable-maintainer-mode and you
  98   will need to update the .class files and generated CNI header files in
  99   your working tree
 100
 101 Over time we plan to remove as many of the remaining divergences as
 102 possible.
 103
 104 File additions and deletions require running scripts/makemake.tcl
 105 before running automake.
 106
 107 --
 108
 109 In general you should not make any changes in the classpath/
 110 directory.  Changes here should come via imports from upstream.
 111 However, there are three (known) exceptions to this rule:
 112
 113 * In an emergency, such as a bootstrap breakage, it is ok to commit a
 114   patch provided that the problem is resolved (by fixing a compiler
 115   bug or fixing the Classpath bug upstream) somehow and the resolution
 116   is later checked in (erasing the local diff).
 117
 118 * On a release branch to fix a bug, where a full-scale import of
 119   Classpath is not advisable.
 120
 121 * We maintain a fair number of divergences in the build system.
 122   This is a pain but they don't seem suitable for upstream.
 123
 124 --
 125
 126 You can develop in a GCC tree using a CVS checkout of Classpath, most
 127 of the time.  (The exceptions are when an incompatible change has been
 128 made in Classpath and some core part of libgcj has not yet been
 129 updated.)
 130
 131 The way to set this up is very similar to importing a new version of
 132 Classpath into the libgcj tree.  In your working tree:
 133
 134 * cd gcc/libjava; rm -rf classpath
 135 * cvs co classpath
 136 * cd classpath
 137   Now run the auto tools as specified in the import process; then
 138   cd ..
 139 * Run 'scripts/makemake.tcl > sources.am' in the source tree
 140 * Run automake for libgcj
 141
 142 Now you should be ready to go.
 143
 144 If you are working in a tree like this, you must remember to run
 145 makemake.tcl and automake whenever you update your embedded classpath
 146 tree.
 147
 148 --
 149
 150 If you add a class to java.lang, java.io, or java.util
 151 (including sub-packages, like java.lang.ref).
 152
 153 * Edit gcj/javaprims.h
 154
 155 * Go to the `namespace java' line, and delete that entire block (the
 156   entire contents of the namespace)
 157
 158 * Then insert the output of `perl scripts/classes.pl' into the file
 159   at that point.  This must be run from the build tree, in
 160   <build>/classpath/lib; it uses the .class file name to determine
 161   what to print.