Contribution guidelines

Thank you for considering contributing to the GLib project!

These guidelines are meant for new contributors, regardless of their level of proficiency; following them allows the core developers of the GLib project to more effectively evaluate your contribution, and provide prompt feedback to you. Additionally, by following these guidelines you clearly communicate that you respect the time and effort that the people developing GLib put into managing the project.

GLib is a complex free software utility library, and it would not exist without contributions from the free and open source software community. There are many things that we value:

• bug reporting and fixing
• documentation and examples
• tests
• testing and support for other platforms
• new features

Please, do not use the issue tracker for support questions. If you have questions on how to use GLib effectively, you can use:

• the #gtk IRC channel on irc.gnome.org
• the glib tag on GNOME's Discourse

You can also look at the glib tag on Stack Overflow.

The issue tracker is meant to be used for actionable issues only.

How to report bugs

Security issues

You should not open a new issue for security related questions.

When in doubt, send an email to the security mailing list.

Bug reports

If you’re reporting a bug make sure to list:

0. which version of GLib are you using?
1. which operating system are you using?
2. the necessary steps to reproduce the issue
3. the expected outcome
4. a description of the behavior
5. a small, self-contained example exhibiting the behavior

If the issue includes a crash, you should also include:

0. the eventual warnings printed on the terminal
1. a backtrace, obtained with tools such as GDB or LLDB

If the issue includes a memory leak, you should also include:

0. a log of definite leaks from a tool such as valgrind’s memcheck

For small issues, such as:

• spelling/grammar fixes in the documentation,
• typo correction,
• comment clean ups,
• changes to metadata files (CI, .gitignore),
• build system changes, or
• source tree clean ups and reorganizations;

or for self-contained bug fixes where you have implemented and tested a solution already, you should directly open a merge request instead of filing a new issue.

Features and enhancements

Feature discussion can be open ended and require high bandwidth channels; if you are proposing a new feature on the issue tracker, make sure to make an actionable proposal, and list:

0. what you’re trying to achieve and the problem it solves
1. three (or more) existing pieces of software which would benefit from the new feature
2. how the feature is implementable on platforms other than Linux

New APIs, in particular, should follow the ‘rule of three’, where there should be three (or more) pieces of software which are ready to use the new APIs. This allows us to check that the new APIs are usable in real-life code, and fit well with related APIs. This reduces the chances of awkward or unusable APIs becoming stable in GLib and having to be supported forever.

A common way to introduce new APIs or data types to GLib is to prototype them in another code base for a while, to gain real-life experience with them before they are imported into GLib and marked as stable.

Each feature should also come fully documented, and with tests which approach full branch coverage of the new code. GLib’s CI system generates code coverage reports which are viewable for each merge request.

If proposing a large feature or change, it’s better to discuss it (on the #gtk IRC channel or on Discourse before putting time into writing an actionable issue — and certainly before putting time into writing a merge request.

Your first contribution

Prerequisites

If you want to contribute to the GLib project, you will need to have the development tools appropriate for your operating system, including:

• Python 3.x
• Meson
• Ninja
• Gettext (19.7 or newer)
• a C99 compatible compiler

Up-to-date instructions about developing GNOME applications and libraries can be found on the GNOME Developer Center.

The GLib project uses GitLab for code hosting and for tracking issues. More information about using GitLab can be found on the GNOME wiki.

Getting started

You should start by forking the GLib repository from the GitLab web UI, and cloning from your fork:

$ git clone https://gitlab.gnome.org/yourusername/glib.git
$ cd glib

Note: if you plan to push changes to back to the main repository and have a GNOME account, you can skip the fork, and use the following instead:

$ git clone git@gitlab.gnome.org:GNOME/glib.git
$ cd glib

To compile the Git version of GLib on your system, you will need to configure your build using Meson:

$ meson _builddir .
$ cd _builddir
$ ninja

Typically, you should work on your own branch:

$ git checkout -b your-branch

Once you’ve finished working on the bug fix or feature, push the branch to the Git repository and open a new merge request, to let the GLib core developers review your contribution.

Code reviews

Each contribution is reviewed by the core developers of the GLib project.

The CODEOWNERS document contains the list of core contributors to GLib and the areas for which they are responsible; you should ensure to receive their review and signoff on your changes.

It is our intention that every commit to GLib is reviewed by at least one other person, including commits from core developers. We all make mistakes and can always learn from each other, and code review allows that. It also reduces bus factor by spreading knowledge of each commit between at least two people.

With each code review, we intend to:

0. Identify if this is a desirable change or new feature. Ideally for larger features this will have been discussed (in an issue, on IRC, or on Discourse) already, so that effort isn’t wasted on putting together merge requests which will be rejected.
1. Check the design of any new API.
2. Provide realistic estimates of how long a review might take, if it can’t happen immediately.
3. Ensure that all significant contributions of new code, or bug fixes, are adequately tested, either through requiring tests to be submitted at the same time, or as a follow-up.
4. Ensure that all new APIs are documented and have introspection annotations.
5. Check that the contribution is split into logically separate commits, each with a good commit message.
6. Encourage further high quality contributions.
7. Ensure code style and quality is upheld.

If a code review is stalled (due to not receiving comments for two or more weeks; or due to a technical disagreement), please ping another GLib core developer on the merge request, or on IRC, to ask for a second opinion.

Commit messages

The expected format for git commit messages is as follows:

Short explanation of the commit

Longer explanation explaining exactly what’s changed, whether any
external or private interfaces changed, what bugs were fixed (with bug
tracker reference if applicable) and so forth. Be concise but not too
brief.

Closes #1234

• Always add a brief description of the commit to the first line of the commit and terminate by two newlines (it will work without the second newline, but that is not nice for the interfaces).

• First line (the brief description) must only be one sentence and should start with a capital letter unless it starts with a lowercase symbol or identifier. Don’t use a trailing period either. Don’t exceed 72 characters.

• The main description (the body) is normal prose and should use normal punctuation and capital letters where appropriate. Consider the commit message as an email sent to the developers (or yourself, six months down the line) detailing why you changed something. There’s no need to specify the how: the changes can be inlined.

• When committing code on behalf of others use the --author option, e.g. git commit -a --author "Joe Coder <joe@coder.org>" and --signoff.

• If your commit is addressing an issue, use the GitLab syntax to automatically close the issue when merging the commit with the upstream repository:

Closes #1234
Fixes #1234
Closes: https://gitlab.gnome.org/GNOME/glib/issues/1234

• If you have a merge request with multiple commits and none of them completely fixes an issue, you should add a reference to the issue in the commit message, e.g. Bug: #1234, and use the automatic issue closing syntax in the description of the merge request.

Merge access to the GLib repository

GLib is part of the GNOME infrastructure. At the current time, any person with write access to the GNOME repository can merge merge requests to GLib. This is a good thing, in that it allows maintainership to be delegated and shared as needed. However, GLib is a fairly large and complicated package that many other things depend on, and which has platform specific behavior — so to avoid unnecessary breakage, and to take advantage of the knowledge about GLib that has been built up over the years, we’d like to ask people contributing to GLib to follow a few rules:

0. Never push to the main branch, or any stable branches, directly; you should always go through a merge request, to ensure that the code is tested on the CI infrastructure at the very least. A merge request is also the proper place to get a comprehensive code review from the core developers of GLib.

1. Always get a code review, even for seemingly trivial changes.

2. Pay attention to the CI results. Merge requests cannot be merged until the CI passes. If they consistently fail, either something is wrong with the change, or the CI tests need fixing — in either case, please bring this to the attention of a core developer rather than overriding the CI.

If you have been contributing to GLib for a while and you don’t have commit access to the repository, you may ask to obtain it following the GNOME account process.