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. Please build with warnings enabled. Install the dependencies from the `installation instructions `_, then run: .. code-block:: console $ git clone https://github.com/osandov/drgn.git $ cd drgn $ CONFIGURE_FLAGS="--enable-compiler-warnings=error" python3 setup.py build_ext -i $ python3 -m drgn --help Testing ------- Tests should be added for all features and bug fixes. drgn's test suite can be run with: .. code-block:: console $ python3 setup.py test To run Linux kernel helper tests in a virtual machine on all supported kernels, add ``-K``. See `vmtest `_ for more details. Tests can also be run manually with `unittest `_ after building locally: .. code-block:: console $ 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 `_. Only the CLI and helpers should be in pure Python. C ^ C code in drgn mostly follows the `Linux kernel coding style `_ except that drgn requires C11 or newer, so declarations may be mixed with code. A few other guidelines/conventions: * Constants should be defined as enums or ``static const`` variables rather than macros. * 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) and be the last parameter(s) of the function. * Functions that initialize an already allocated structure should be suffixed with ``_init`` and take the structure to initialize as the first argument, e.g., ``struct drgn_error *foo_init(struct foo *foo, int foo_flags)``. * The matching function to deinitialize a structure should be suffixed with ``_deinit``, e.g., ``void foo_deinit(struct foo *foo)``. If possible, the definition should be placed directly after the definition of ``_init`` so that it is easier to visually verify that everything is cleaned up. * Functions that allocate and initialize a structure should be suffixed with ``_create`` and either return the structure as an out parameter (e.g., ``struct drgn_error *foo_create(int foo_flags, struct foo **ret)``) or as the return value if they can only fail with an out-of-memory error (e.g., ``struct foo *foo_create(int foo_flags)``). * The matching function to free an allocated structure should be suffixed with ``_destroy``, e.g., ``void foo_destroy(struct foo *foo)``. If possible, the definition should be placed directly after the definition of ``_create``. ``_destroy`` should usually allow a ``NULL`` argument, just like ``free()``. * Functions that return a result in a ``struct drgn_object *`` parameter should only modify the object if the function succeeds. drgn assumes some `implementation-defined behavior `_ 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 should be compatible with Python 3.6 and newer. Python code should be formatted with `Black `_ and `isort `_ and checked with `flake8 `_. Type hints should be provided for all interfaces (including helpers and the C extension). Linux Kernel Helpers ^^^^^^^^^^^^^^^^^^^^ Linux kernel helpers should work on all `supported kernels `_ if possible. This may require handling changes between kernel releases. * Do NOT check the kernel version number to do this; Linux distributions often backport changes without updating the version number. Instead, use the presence or absence of variables, types, structure members, etc. * Optimize for the latest kernel release, and follow "easier to ask for forgiveness than permission" (`EAFP `_). For example, assume that a structure member from the latest release exists and catch the exception if it doesn't. * Reference the diverging commit and version number in the format ``Linux kernel commit $abbreviated_commit_hash "$commit_subject" (in v$kernel_version)``. For example: .. code-block:: python3 # Since Linux kernel commit 2f064a59a11f ("sched: Change # task_struct::state") (in v5.14), the task state is named "__state". # Before that, it is named "state". try: return task.__state except AttributeError: return task.state NOT: .. code-block:: python3 # BAD if hasattr(task, "state"): return task.state else: return task.__state * Document the expected C types of arguments and return values. For example: .. code-block:: python3 def cgroup_parent(cgrp: Object) -> Object: """ Return the parent cgroup of the given cgroup if it exists, ``NULL`` otherwise. :param cgrp: ``struct cgroup *`` :return: ``struct cgroup *`` """ ... pre-commit ^^^^^^^^^^ Some of these guidelines are checked by automated builds for pull requests. If you'd like to run the checks locally prior to submission, you can install `pre-commit `_: .. code-block:: console $ pip install pre-commit Then, you can either install the checks as Git hooks so that they're run when creating a commit: .. code-block:: console $ pre-commit install --install-hooks Or you can run them manually: .. code-block:: console $ pre-commit run --all-files Submitting PRs -------------- Pull requests and issues are always welcome. Feel free to start a discussion with a prototype. Signing Off ^^^^^^^^^^^ All commits must be signed off (i.e., ``Signed-off-by: Jane Doe ``) as per the `Developer Certificate of Origin `_. ``git commit -s`` can do this for you. Separating Changes ^^^^^^^^^^^^^^^^^^ Each logical change should be a separate commit. For example, if a PR adds new functionality to the core library and a new helper that uses the new functionality, the core change and the helper should be separate commits. This makes code review much easier. Each commit should build, pass tests, follow coding guidelines, and run correctly. (In other words, within a PR, later commits often build on top of earlier commits, but later commits shouldn't need to "fix" earlier commits.) This makes it easier to track down problems with tools like ``git bisect`` which may check out any commit in the middle of a PR. Commit Messages ^^^^^^^^^^^^^^^ The template for a good commit message is: .. code-block:: none One line summary Longer explanation including more details, background, and/or motivation. Signed-off-by: Jane Doe See `this post `_ for more information about writing good commit messages.