Contributing
============

Thanks for your interest in drgn! See below for how to build, test, code, and
submit changes for drgn.

Building
--------

The easiest way to develop drgn is by building and running it locally. See the
`installation documentation
<https://drgn.readthedocs.io/en/latest/installation.html#development>`_.

Testing
-------

.. highlight:: console

Tests should be added for all features and bug fixes.

drgn's test suite can be run with::

    $ python3 setup.py test

To run Linux kernel helper tests in a virtual machine on all supported kernels,
add ``-K``. See `vmtest <vmtest/README.rst>`_ for more details.

Tests can also be run manually with `unittest
<https://docs.python.org/3/library/unittest.html#command-line-interface>`_
after building locally::

    $ python3 -m unittest discover -v

To run Linux kernel helper tests on the running kernel, this must be run as
root, and debug information for the running kernel must be available.

Coding Guidelines
-----------------

* Core functionality should be implemented in ``libdrgn`` and exposed to Python
  via the `C extension <libdrgn/python>`_. Only the CLI and helpers should be
  in pure Python.
* Linux kernel helpers should work on all supported kernels if possible.

C
^

C code in drgn mostly follows the `Linux kernel coding style
<https://www.kernel.org/doc/html/latest/process/coding-style.html>`_ except
that drgn requires C11 or newer, so declarations may be mixed with code.

A few other guidelines:

* Functions that can fail should return a ``struct drgn_error *`` (and return
  their result via an out parameter if necessary).
* Out parameters should be named ``ret`` (or suffixed with ``_ret`` if there
  are multiple).
* Constants should be defined as enums or ``static const`` variables rather
  than macros.

drgn assumes some `implementation-defined behavior
<https://gcc.gnu.org/onlinedocs/gcc/C-Implementation.html>`_ for sanity:

* Signed integers are represented with two's complement.
* Bitwise operators on signed integers operate on the two's complement
  representation.
* Right shift of a signed integer type is arithmetic.
* Conversion to a signed integer type is modular.
* Casting between pointers and integers does not change the bit representation.

Python
^^^^^^

Python code in drgn is formatted with `black <https://github.com/psf/black>`_.
Code should be compatible with Python 3.6 and newer.

Type hints should be provided for all public interfaces other than helpers
(including the C extension) and most private interfaces.

Submitting PRs
--------------

Pull requests and issues are always welcome. Feel free to start a discussion
with a prototype.

All commits must be signed off (i.e., ``Signed-off-by: Jane Doe
<janedoe@example.org>``) as per the `Developer Certificate of Origin
<https://developercertificate.org/>`_. ``git commit -s`` can do this for you.