Avoid using global variables in programs

[gromacs.git] / docs / dev-manual / uncrustify.rst

.. _gmx-uncrustify:

Automatic source code formatting
================================

.. highlight:: bash

The source code can be automatically formatted using uncrustify, an automatic
source code formatting tool, to follow the guidelines in
:doc:`formatting`.
Additionally, Python scripts are used for a few other automatic
formatting/checking tasks.  The overview tools page contains a list of these
tools: :ref:`dev-formatting-tools`.
This page provides more details for uncrustify and copyright scripts.

Jenkins uses these same scripts (in particular, ``uncrustify.sh`` and the
``check-source`` target) to enforce that the code stays invariant under such
formatting.

Setting up uncrustify
---------------------

A patched version of uncrustify is used for |Gromacs|.  To set this up, you need
to do these (once):

1. Change to a directory under which you want to build uncrustify and run::

     git clone -b gromacs git://github.com/rolandschulz/uncrustify.git
     cd uncrustify
     ./configure
     make

2. Copy the binary ``src/uncrustify`` into a directory of your choice
   (``/path/to/uncrustify`` below).

Alternatively, if you are running Linux, you can try whether the binary from
http://redmine.gromacs.org/issues/845 works for you.

In order to use the binary for ``uncrustify.sh`` and for the pre-commit hook, you
also need to run this in each of your |Gromacs| repositories::

  git config hooks.uncrustifypath /path/to/uncrustify

Alternatively, if you just want to use ``uncrustify.sh``, you can set the
``UNCRUSTIFY`` environment variable to ``/path/to/uncrustify``.

Using the pre-commit hook or git filters needs additional setup; see the
respective sections below.

What is automatically formatted?
--------------------------------

To identify which files are subject to automatic formatting, the scripts use
git filters, specified in ``.gitattributes`` files.  Only files that have the
attribute ``filter`` set to one of the below values are processed:

- ``filter=uncrustify``: uncrustify is run, copyright headers are checked, and
  include order is enforced
- ``filter=uncrustify_only``: only uncrustify is run
- ``filter=includesort``: include order is enforced and copyright headers are
  checked
- ``filter=copyright``: only copyright headers are checked

Other files are ignored by ``uncrustify.sh`` and ``reformat_all.sh`` scripts (see
below).


Scripts
-------

``copyright.py``
^^^^^^^^^^^^^^^^

This script provides low-level functionality to check and update copyright
headers in C/C++ source files, as well as in several other types of files like
CMake and Python scripts.

This file is also used as a loadable Python module for kernel generators, and
provides the functionality to generate conformant copyright headers for such
scripts.

The script is similar to uncrustify in that there is rarely need to run it
directly, but instead the bash scripts below use it internally.  You can run
the script with ``--help`` option if you want to see what all options it provides
if you need to do some maintenance on the copyright headers themselves.

``uncrustify.sh``
^^^^^^^^^^^^^^^^^

This script runs uncrustify and ``copyright.py`` on modified files and
reports/applies the results.
By default, the current HEAD commit is compared to the work tree,
and files that

1. are different between these two trees and
2. change under uncrustify and/or have outdated copyright header

are reported.  This behavior can be changed by

1. Specifying an ``--rev=REV`` argument, which uses ``REV`` instead of HEAD as
   the base of the comparison.  A typical use case is to specify ``--rev=HEAD^``
   to check the HEAD commit.
2. Specifying an action:

   - ``check-*``:   reports the files that uncrustify changes
   - ``diff-*``:    prints the actual diff of what would change
   - ``update-*``:  applies the changes to the repository
   - ``*-workdir``: operates on the working directory (files on disk)
   - ``*-index``:   operates on the index of the repository

   For convenience, if you omit the workdir/index suffix, workdir is assumed
   (i.e., ``diff`` equals ``diff-workdir``).
3. Specifying ``--uncrustify=off``, which does not run uncrustify.
4. Specifying ``--copyright=<mode>``, which alters the level of copyright
   checking is done:

   ``off``
     does not check copyright headers at all
   ``year``
     only update copyright year in new-format copyright headers
   ``add``
     in addition to ``year``, add copyright headers to files that do not
     have any
   ``update``
     in addition to ``year`` and ``add``, also update new-format copyright
     headers if they are broken or outdated
   ``replace``
     replace any copyright header with a new-format copyright header
   ``full``
     do all of the above

By default, ``update-*`` refuses to update dirty files (i.e., that differ
between the disk and the index) to make it easy to revert the changes.
This can be overridden by adding a ``-f``/``--force`` option.

git pre-commit hook
^^^^^^^^^^^^^^^^^^^

If you want to run ``uncrustify.sh`` automatically for changes you make, you can
configure a pre-commit hook using ``admin/git-pre-commit``:

1. Copy the ``git-pre-commit`` script to .git/hooks/pre-commit.
2. Specify the path to uncrustify for the hook if you have not already done
   so::

     git config hooks.uncrustifypath /path/to/uncrustify

3. Set the operation mode for the hook::

     git config hooks.uncrustifymode check
     git config hooks.copyrightmode  update

With this configuration, all source files modified in the commit are run
through uncrustify and checked for correct copyright headers.
If any file would be changed by ``uncrustify.sh``, the names of those files are
reported and the commit is prevented.  The issues can be fixed by running
``uncrustify.sh`` manually.

To disable the hook without removing the ``pre-commit`` file, you can set ::

  git config hooks.uncrustifymode off
  git config hooks.copyrightmode off

To disable it temporarily for a commit, set NO_FORMAT_CHECK environment
variable.  For example, ::

    NO_FORMAT_CHECK=1 git commit -a

You can also run ``git commit --no-verify``, but that also disables other hooks,
such as the Change-Id ``commit-msg`` hook used by Gerrit.

Note that when you run ``git commit --amend``, the hook is only run for the
changes that are getting amended, not for the whole commit.  During a rebase,
the hook is not run.

The actual work is done by the ``admin/uncrustify.sh`` script, which gets
run with the ``check-index`` action, and with ``--uncrustify`` and ``--copyright``
getting set according to the ``git config`` settings.

``reformat_all.sh``
^^^^^^^^^^^^^^^^^^^

This script runs uncrustify, ``copyright.py``, or the include sorter for all
applicable files in the source tree.  See ``reformat_all.sh -h`` for the
invocation.

The script can also produce the list of files for which these commands would be
run.  To do this, specify ``list-files`` on the command line and use
``--filter=<type>`` to specify which command to get the file list for.  This can
be used together with, e.g., ``xargs`` to run other scripts on the same set of
files.

For all the operations, it is also possible to apply patters (of the same style
that various git commands accept, i.e., ``src/*.cpp`` matches all ``.cpp`` files
recursively under ``src/``).  The patterns can be specified with
``--pattern=<pattern>``, and multiple ``--pattern`` arguments can be given.

As with ``uncrustify.sh``, ``-f``/``--force`` is necessary if the working tree and
the git index do not match.


Using git filters
-----------------

An alternative to using a pre-commit hook to automatically apply uncrustify on
changes is to use a git filter (does not require ``uncrustify.sh``, only the
``.gitattributes`` file).  You can run ::

  git config filter.uncrustify.clean \
      "/path/to/uncrustify -c admin/uncrustify.cfg -q -l cpp"

To configure a filter for all files that specify ``filter=uncrustify`` attribute.

The pre-commit hook + manually running ``uncrustify.sh`` gives better/more
intuitive control (with the filter, it is possible to have a work tree that is
different from HEAD and still have an empty ``git diff``) and provides better
performance for changes that modify many files.  It is the only way that
currently also checks the copyright headers.

The filter allows one to transparently merge branches that have not been run
through uncrustify, and is applied more consistently (the pre-commit hook is
not run for every commit, e.g., during a rebase).