The guidelines in this file are the ideals; it's better to send a not-fully-following-guidelines patch than no patch at all, though. We can always polish it up.
Source code and issue tracking for the D-Bus specification and its reference implementation ‘dbus’ are provided by freedesktop.org Gitlab: https://gitlab.freedesktop.org/dbus/dbus.
If you find a security vulnerability that is not known to the public, please report it privately to dbus-security@lists.freedesktop.org or by reporting a Gitlab issue at https://gitlab.freedesktop.org/dbus/dbus/issues/new and marking it as “confidential”.
The D-Bus mailing list is dbus@lists.freedesktop.org; discussion of protocol enhancements, new implementations, etc. should go there.
As a freedesktop.org project, dbus follows the Contributor Covenant, found at: https://www.freedesktop.org/wiki/CodeOfConduct
Please conduct yourself in a respectful and civilised manner when interacting with community members on mailing lists, IRC, or bug trackers. The community represents the project as a whole, and abusive or bullying behaviour is not tolerated by the project.
D-Bus uses Git as its version control system. The main repository is hosted on freedesktop.org Gitlab. To clone D-Bus, execute one of the following commands:
git clone https://gitlab.freedesktop.org/dbus/dbus.git git clone git@gitlab.freedesktop.org:dbus/dbus.git
The second form is the one that allows pushing, but it also requires an SSH account on the server. The first form allows anonymous checkouts.
D-Bus development happens in multiple branches in parallel. The main branches are the current stable branch, with an even minor number (like 1.0, 1.2 and 1.4), and the next development branch, with the next odd number. At the time of writing, the stable branch is dbus 1.12.x and the development branch is dbus 1.13.x, leading to a new 1.14.x stable branch in future.
Stable branches are named after the version number itself (dbus-1.2, dbus-1.4), whereas the development branch is simply known as master.
New features, enhancements, minor bug fixes, and bug fixes that are unusually intrusive should always be based on the master branch.
Fixes for significant bugs should be developed on the master branch and cherry-picked to the most recent stable branch.
Depending on the release cycles of various Linux distributions, some older stable branches might continue to receive fixes for security vulnerabilities (and sometimes major non-security bugs) for a time. These are announced on the D-Bus mailing list.
Old development branches are not supported at all, and will not receive any bug fixes - not even for security vulnerabilities. Please do not use a development branch like 1.13.x in your OS distribution, unless you can guarantee that you will upgrade to the next stable branch such as 1.14.x when it becomes available.
If you are making changes that you wish to be incorporated upstream, please do as small commits to your local git tree that are individually correct, so there is a good history of your changes.
The first line of the commit message should be a single sentence that describes the change, optionally with a prefix that identifies the area of the code that is affected.
The body of the commit message should describe what the patch changes and why, and also note any particular side effects. This shouldn‘t be empty on most of the cases. It shouldn’t take a lot of effort to write a commit message for an obvious change, so an empty commit message body is only acceptable if the questions “What?” and “Why?” are already answered on the one-line summary.
The lines of the commit message should have at most 76 characters, to cope with the way git log presents them.
See notes on commit messages, A Note About Git Commit Messages or How to Write a Git Commit Message for recommended reading on writing high-quality commit messages.
Your patches should also include a Signed-off-by line with your name and email address, indicating that your contribution follows the Developer's Certificate of Origin. If you‘re not the patch’s original author, you should also gather S-o-b's by them (and/or whomever gave the patch to you.) The significance of this is that it certifies that you created the patch, that it was created under an appropriate open source license, or provided to you under those terms. This lets us indicate a chain of responsibility for the copyright status of the code.
We won't reject patches that lack S-o-b, but it is strongly recommended.
When you consider your changes to be ready for merging to mainline:
Most of D-Bus is security sensitive. Guidelines related to that:
avoid memcpy(), sprintf(), strlen(), snprintf(), strlcat(), strstr(), strtok(), or any of this stuff. Use DBusString. If DBusString doesn't have the feature you need, add it to DBusString.
There are some exceptions, for example if your strings are just used to index a hash table and you don‘t do any parsing/modification of them, perhaps DBusString is wasteful and wouldn’t help much. But definitely if you're doing any parsing, reallocation, etc. use DBusString.
do not include system headers outside of dbus-memory.c, dbus-sysdeps.c, and other places where they are already included. This gives us one place to audit all external dependencies on features in libc, etc.
do not use libc features that are “complicated” and may contain security holes. For example, you probably shouldn't try to use regcomp() to compile an untrusted regular expression. Regular expressions are just too complicated, and there are many different libc implementations out there.
we need to design the message bus daemon (and any similar features) to use limited privileges, run in a chroot jail, and so on.
http://vsftpd.beasts.org/ has other good security suggestions.
Please follow the coding style and indentation of nearby code.
C code uses GNU coding conventions (approximately “gnu” style in Emacs), with GLib-like extensions (e.g. lining up function arguments).
Write docs for all non-static functions and structs and so on. try doxygen Doxyfile prior to commit and try not to cause any new warnings.
All external interfaces (network protocols, file formats, etc.) should have documented specifications sufficient to allow an alternative implementation to be written. Our implementation should be strict about specification compliance (should not for example heuristically parse a file and accept not-well-formed data). Avoiding heuristics is also important for security reasons; if it looks funny, ignore it (or exit, or disconnect).
Please match the existing licensing (a dual-license: AFL-2.1 or GPL-2+, recipient's choice). Entirely new modules can be placed under a more permissive license: to avoid license proliferation, our preferred permissive license is the variant of the MIT/X11 license used by the Expat XML library (for example see the top of tools/ci-build.sh).
The primary build system for dbus uses the GNU Autotools suite (Autoconf, Automake and Libtool). This build system is strongly recommended for Unix OS integrators. It can also be used to compile dbus for Windows using the mingw-w64 compiler suite, either by cross-compiling on a Unix system or by using an environment like MSYS2 on Windows.
There is also a CMake build system. This is primarily there to make it easier to build dbus on Windows, using either a MSYS2/mingw environment or the MSVC compiler from Microsoft Visual Studio. It can also be used on a GNU/Linux system, but this is not recommended for OS integrators.
Changes contributed to dbus must not break the build for either of these build systems. It is OK for the CMake build system to support fewer options, support fewer operating systems, have less test coverage or build fewer non-essential programs, but it must continue to work on at least GNU/Linux and Windows.
These are some of the environment variables that are used by the D-Bus client library.
DBUS_VERBOSE=1
Turns on printing verbose messages. This only works if D-Bus has been compiled with --enable-verbose-mode.
DBUS_MALLOC_FAIL_NTH=n
Can be set to a number, causing every nth call to dbus_alloc or dbus_realloc to fail. This only works if D-Bus has been compiled with --enable-embedded-tests.
DBUS_MALLOC_FAIL_GREATER_THAN=n
Can be set to a number, causing every call to dbus_alloc or dbus_realloc to fail if the number of bytes to be allocated is greater than the specified number. This only works if D-Bus has been compiled with --enable-embedded-tests.
DBUS_TEST_MALLOC_FAILURES=n
Many of the D-Bus tests will run over and over, once for each malloc involved in the test. Each run will fail a different malloc, plus some number of mallocs following that malloc (because a fair number of bugs only happen if two or more mallocs fail in a row, e.g. error recovery that itself involves malloc). This environment variable sets the number of consecutive mallocs to fail.
Here's why you care: If set to 0, then the malloc checking is skipped, which makes the test suite a lot faster. Just run with this environment variable unset before you commit.
Please try to write test coverage for all new functionality. We have two broad categories of tests.
The modular tests are enabled by configuring with --enable-modular-tests. These mostly use GLib's GTest framework, and are standalone programs that do not affect the contents of the production dbus library and programs. Most of them can be installed alongside the library and programs by configuring with --enable-installed-tests.
The embedded tests are enabled by configuring with --enable-embedded-tests. Unlike the modular tests, enabling the embedded tests adds special code to libdbus and dbus-daemon, some of which may harm performance or security. A production version of dbus that will be included in an operating system should never have the embedded tests enabled.
If possible, new test coverage should be provided via modular tests, preferably using GLib's GTest framework. test/dbus-daemon.c is a good example.
This section is not directly relevant to infrequent contributors.
To make a release of D-Bus, do the following:
check out a fresh copy from Git
verify that the libtool versioning/library soname is changed if it needs to be, or not changed if not
update the file NEWS based on the git history
verify that the version number of dbus-specification.xml is changed if it needs to be; if changes have been made, update the release date in that file
update the AUTHORS file with “make update-authors” if necessary
the version number should have major.minor.micro, even if micro is 0, i.e. “1.0.0” and “1.2.0” not “1.0”/“1.2”; the micro version should be even for releases, and odd for intermediate snapshots
“make distcheck” (DO NOT just “make dist” - pass the check!)
if make distcheck fails, fix it.
once distcheck succeeds, “git commit -a”. This is the version of the tree that corresponds exactly to the released tarball.
tag the tree with “git tag -s -m ‘Released X.Y.Z’ dbus-X.Y.Z” where X.Y.Z is the version of the release. If you can't sign then simply created an unsigned annotated tag: “git tag -a -m ‘Released X.Y.Z’ dbus-X.Y.Z”.
bump the version number up in configure.ac (so the micro version is odd), and commit it. Make sure you do this after tagging the previous release! The idea is that git has a newer version number than anything released. Similarly, bump the version number of dbus-specification.xml and set the release date to “(not finalized)”.
merge the branch you‘ve released to the chronologically-later branch (usually “master”). You’ll probably have to fix a merge conflict in configure.ac (the version number).
push your changes and the tag to the central repository with git push origin master dbus-X.Y dbus-X.Y.Z
scp your tarball to freedesktop.org server and copy it to dbus.freedesktop.org:/srv/dbus.freedesktop.org/www/releases/dbus/dbus-X.Y.Z.tar.gz. This should be possible if you're in group “dbus”
Update the online documentation with make -C doc maintainer-upload-docs.
update the wiki page http://www.freedesktop.org/Software/dbus by adding the new release under the Download heading. Then, cut the link and changelog for the previous that was there.
post to dbus@lists.freedesktop.org announcing the release.
We create a branch for each stable release. The branch name should be dbus-X.Y which is a branch that has releases versioned X.Y.Z; changes on a stable branch should be limited to significant bug fixes.
Because we won't make minor changes like keeping up with the latest deprecations on a stable branch, stable branches should turn off the gcc warning for deprecated declarations (e.g. see commit 4ebb275ab7).
Be extra-careful not to merge master (or any branch based on master) into a stable branch.
To branch:
git branch dbus-X.Y
and upload the branch tag to the server:
git push origin dbus-X.Y
To develop in this branch:
git checkout dbus-X.Y
The commit rules are approximately these:
Fixes that don't affect API or protocol can be committed if any one qualified reviewer other than patch author reviews and approves
For fixes that do affect API or protocol, two people in the reviewer group have to review and approve the commit.
If there‘s a live unresolved controversy about a change, don’t commit it while the argument is still raging.
At their discretion, members of the reviewer group may also commit branches/patches under these conditions:
the branch does not add or change API, ABI or wire-protocol
the branch solves a known problem and is covered by the regression tests
there are no objections from the rest of the review group within a week of the merge request being opened
the committer gets a positive review on the merge request from someone they consider qualified to review the change (e.g. a colleague with D-Bus experience; not necessarily a member of the reviewer group)
Regardless of reviews, to commit a patch:
make check must passNo reviewer should approve a patch without these attributes, and failure on these points is grounds for reverting the patch.
The reviewer group that can approve patches consists of the members of https://gitlab.freedesktop.org/dbus/dbus/project_members with “Maintainer” or “Owner” status.