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Contributing to ccache

Want to contribute to ccache? Awesome!

Asking a question?

There are several options:

  1. Ask a question in discussions.
  2. Post your question to the mailing list.
  3. Chat in the Gitter room.

Reporting an issue?

Please include at least the following information in your bug report:

  1. Which version of ccache you use.
  2. Which compiler you use, if applicable.
  3. Which operating system you use, if applicable.
  4. The problematic behavior you experienced (actual behavior).
  5. How you would like ccache to behave instead (expected behavior).
  6. Steps to reproduce the problematic behavior.

Also, consider reading Effective Ways to Get Help from Maintainers.

Contributing code?

The preferred way is to create one or several pull request with your proposal(s) on GitHub.

Here are some hints to make the process smoother:

  • Have a look in for an overview of the source code tree.
  • If you plan to implement major changes it is wise to open an issue on GitHub (or ask in the Gitter room, or send a mail to the mailing list) asking for comments on your plans before doing the bulk of the work. That way you can avoid potentially wasting time on doing something that may need major rework to be accepted, or maybe doesn't end up being accepted at all.
  • Is your pull request "work in progress", i.e. you don't think that it's ready for merging yet but you want early comments and CI test results? Then create a draft pull request as described in this Github blog post.
  • Please add test cases for your new changes if applicable.
  • Please follow the ccache's code style (see the section below).

Commit message conventions

It is preferable, but not mandatory, to format commit messages in the spirit of Conventional Commits. The commit message subject should look like this:

    <type>: <description>
    <type>(<scope>): <description>

<description> is a succinct description of the change:

  • Use the imperative, present tense: "Change", not "Changed" nor "Changes".
  • Capitalize the first letter.
  • No dot (.) at the end.

Here is a summary of types used for ccache:

Type Explanation
build A change of the build system or build configuration.
bump An increase of the version of an external dependency or an update of a bundled third party package.
chore A change that doesn't match any other type.
ci A change of CI scripts or configuration.
docs A change of documentation only.
enhance An enhancement of the code without adding a user-visible feature, for example adding a new utility class to be used by a future feature or refactoring.
feat An addition or improvement of a user-visible feature.
fix A bug fix (not necessarily user-visible).
perf A performance improvement.
refactor A restructuring of the existing code without changing its external behavior.
style A change of code style.
test An addition or modification of tests or test framework.

Code style

Source code formatting is defined by .clang-format in the root directory. The format is loosely based on LLVM's code formatting style with some exceptions. Run make format (or ninja format if you use Ninja) to format changes according to ccache's code style. Or even better: set up your editor to run <ccache-top-dir>/misc/clang-format (or any other Clang-Format version 10 binary) automatically when saving. Newer Clang-Format versions likely also work fine.

Please follow these conventions:

  • Use UpperCamelCase for types (e.g. classes and structs).
  • Use UPPER_CASE names for macros and (non-class) enum values.
  • Use snake_case for other names (namespaces, functions, variables, enum class values, etc.). (Namespaces used to be in UpperCamelCase; transition is work in progress.)
  • Use an m_ prefix for non-public member variables.
  • Use a g_ prefix for global mutable variables.
  • Use a k_ prefix for global constants.
  • Always use curly braces around if/for/while/do bodies, even if they only contain one statement.