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Comm-central source code (Mercurial)

Mercurial is a source code management tool which allows users to keep track of changes to the source code locally and share their changes with others. The Mozilla project is in transition from using CVS for Mozilla 1.9 development to Mercurial for Mozilla 1.9.1 development and onwards.

If you want to build Thunderbird 2.0, SeaMonkey 1.1, or older versions, use CVS.

Client Settings

The settings are the same as for the core Firefox 3.5/xulrunner 1.9.1 development. See


Getting comm-central source code


comm-central has various different branches available. Current possibilities are:

For more information on these branches, see the comm-central page.

Initial checkout

The Thunderbird, SeaMonkey, Lightning, and Sunbird source code is contained in several different repositories. The main integration repository for those applications is comm-central and contains the main code that is required on top of the core Gecko code. It also contains a script, client.py, which is used to get the other code.

To get one of the comm-central repositories ("clone" the repository, using Mercurial terminology), do the following, replacing <location of repository> with one of the http urls from the branches section above, according to what you want to build:

# Pull the Mozilla source to the folder src/ - may take a while 
# as hundreds of megabytes of history is downloaded to .hg
hg clone <location of repository> src

cd src
If you already have a mozilla-central tree, you can at this stage clone it to src/mozilla to avoid pulling all of mozilla-central again.

Update/pull all other needed sources using client.py:

python client.py checkout
  • If you get the error message "No module named subprocess", install python 2.4 or later.
  • This step will download hundreds of megabytes of data. This can take a while, depending on your network connection.

client.py performs the following tasks:

  • Pulls any new changesets to the comm-central codebase
  • Pulls the mozilla-central codebase into mozilla/
  • Pulls the following repositories into mozilla/extensions/ :
    • irc (Chatzilla)
    • inspector (DOM Inspector)
    • venkman (JavaScript Debugger)
  • Pulls the LDAP SDK codebase into ldap/sdks/
    • (Except on recent trunk — December 2010 — this is done by CVS and the destination is mozilla/directory/c-sdk instead)
  • Runs an hg update after each of the above hg pulls to update the corresponding repository clone's working directory contents. This is not required (in fact, you may prefer to pull manually). Pass --skip-comm to client.py to skip this.
Pulling in the related repositories means that you can use the same source directories to develop and build any of the items mentioned above, but does not mean that you can create cross-repository change sets. Patches that span repositories will require multiple changesets.

Updating the Repository

To update the repository, just run client.py again:

python client.py checkout


For the comm-central apps, see the following links:


The following script will run the checkout, build, and package operations in turn, telling you what it does (and when) and stopping at (and displaying) the first nonzero program exit code. It is written for the bash shell on Linux-i686 and for an object directory set with mk_add_options MOZ_OBJDIR=@TOPSRCDIR@/obj-@CONFIG_GUESS@ but it can be easily adapted for other Mozilla building environments:

# set the following to the actual location of your objdir
# if you want to package an installable archive
export MY_OBJDIR=obj-i686-pc-linux-gnu
date && \
echo 'python client.py checkout' && \
python client.py checkout && \
date && \
echo 'make -f client.mk build' && \
make -f client.mk build && \
test -n "$MY_OBJDIR" -a -d $MY_OBJDIR && \
date && \
echo "make -C $MY_OBJDIR package" && \
make -C $MY_OBJDIR package
echo 'Exit status' $?

Firefox and xulrunner

You can, if needed, build Firefox or xulrunner from this tree. As client.py pulls the mozilla-central repository, builds and development of Firefox and xulrunner can take place within a repository from comm-central. The only difference is that you will need to go into the mozilla/ directory before running the build command:

cd src/mozilla
make -f client.mk build

See Also

Document Tags and Contributors

Last updated by: bsmedberg,