systemd/.github/copilot-instructions.md

systemd AI Coding Agent Instructions

Project Overview

systemd is a system and service manager for Linux, written in C (GNU17 with extensions). The project is built with Meson and consists of ~140 components including PID 1, journald, udevd, networkd, and many other system daemons.

Key Files & Directories

Always include the following files in the context:

• code organization details
• development workflow deep dive
• full style guide

Include any other files from the documentation in the context as needed based on whether you think it might be helpful to solve your current task or help to review the current PR.

Build + Test instructions

CRITICAL: Read and follow these instructions exactly.

• NEVER compile individual files or targets. ALWAYS run mkosi -f box meson compile -C build to build the entire project. Meson handles incremental compilation automatically.
• NEVER run meson compile followed by meson test as separate steps. ALWAYS run mkosi -f box meson test -C build -v <TEST-NAME> directly. Meson will automatically rebuild any required targets before running tests.
• NEVER invent your own build commands or try to optimize the build process.
• NEVER use head, tail, or pipe (|) the output of build or test commands. Always let the full output display. This is critical for diagnosing build and test failures.
• When asked to build and test code changes:
  • CORRECT: Run mkosi -f box -- meson test -C build -v <TEST-NAME> (this builds and runs tests in one command)
  • WRONG: Run mkosi -f box -- meson compile -C build followed by mkosi -f box -- meson test -C build -v <TEST-NAME>
  • WRONG: Run mkosi -f box -- meson compile -C build src/core/systemd or similar individual target compilation
  • WRONG: Run mkosi -f box -- meson test -C build -v <TEST-NAME> 2>&1 | tail -100 or similar piped commands

Pull Request review instructions

• Focus on making sure the coding style is followed as documented in docs/CODING_STYLE.md
• Only leave comments for logic issues if you are very confident in your deduction
• Frame comments as questions
• Always consider you may be wrong
• Do not argue with contributors, assume they are right unless you are very confident in your deduction
• Be extremely thorough. Every single separate coding style violation should be reported

Testing Expectations

• Unit tests for self contained functions with few dependencies
• Integration tests for system-level functionality
• CI must pass (build + unit + integration tests)
• Code coverage tracked via Coveralls

Integration with Development Tools

• clangd: Use mkosi.clangd script to start a C/C++ LSP server for navigating C source and header files. Run mkosi -f box -- meson setup build && mkosi -f box -- meson compile -C build gensources first to prepare the environment.

AI Contribution Disclosure

Per project policy: If you use AI code generation tools, you must disclose this in commit messages and PR descriptions. All AI-generated output requires thorough human review before submission.