docs/ClangFormat.rst

===========
ClangFormat
===========

`ClangFormat` describes a set of tools that are built on top of
:doc:`LibFormat`. It can support your workflow in a variety of ways including a
standalone tool and editor integrations.


Standalone Tool
===============

:program:`clang-format` is located in `clang/tools/clang-format` and can be used
to format C/C++/Obj-C code.

.. code-block:: console

  $ clang-format -help
  OVERVIEW: A tool to format C/C++/Obj-C code.

  If no arguments are specified, it formats the code from standard input
  and writes the result to the standard output.
  If <file>s are given, it reformats the files. If -i is specified
  together with <file>s, the files are edited in-place. Otherwise, the
  result is written to the standard output.

  USAGE: clang-format [options] [<file> ...]

  OPTIONS:

  Clang-format options:

    -cursor=<uint>           - The position of the cursor when invoking
                               clang-format from an editor integration
    -dump-config             - Dump configuration options to stdout and exit.
                               Can be used with -style option.
    -i                       - Inplace edit <file>s, if specified.
    -length=<uint>           - Format a range of this length (in bytes).
                               Multiple ranges can be formatted by specifying
                               several -offset and -length pairs.
                               When only a single -offset is specified without
                               -length, clang-format will format up to the end
                               of the file.
                               Can only be used with one input file.
    -lines=<string>          - <start line>:<end line> - format a range of
                               lines (both 1-based).
                               Multiple ranges can be formatted by specifying
                               several -lines arguments.
                               Can't be used with -offset and -length.
                               Can only be used with one input file.
    -offset=<uint>           - Format a range starting at this byte offset.
                               Multiple ranges can be formatted by specifying
                               several -offset and -length pairs.
                               Can only be used with one input file.
    -output-replacements-xml - Output replacements as XML.
    -style=<string>          - Coding style, currently supports:
                                 LLVM, Google, Chromium, Mozilla, WebKit.
                               Use -style=file to load style configuration from
                               .clang-format file located in one of the parent
                               directories of the source file (or current
                               directory for stdin).
                               Use -style="{key: value, ...}" to set specific
                               parameters, e.g.:
                                 -style="{BasedOnStyle: llvm, IndentWidth: 8}"

  General options:

    -help                    - Display available options (-help-hidden for more)
    -help-list               - Display list of available options (-help-list-hidden for more)
    -version                 - Display the version of this program


Vim Integration
===============

There is an integration for :program:`vim` which lets you run the
:program:`clang-format` standalone tool on your current buffer, optionally
selecting regions to reformat. The integration has the form of a `python`-file
which can be found under `clang/tools/clang-format/clang-format.py`.

This can be integrated by adding the following to your `.vimrc`:

.. code-block:: vim

  map <C-K> :pyf <path-to-this-file>/clang-format.py<CR>
  imap <C-K> <ESC>:pyf <path-to-this-file>/clang-format.py<CR>i

The first line enables :program:`clang-format` for NORMAL and VISUAL mode, the
second line adds support for INSERT mode. Change "C-K" to another binding if
you need :program:`clang-format` on a different key (C-K stands for Ctrl+k).

With this integration you can press the bound key and clang-format will
format the current line in NORMAL and INSERT mode or the selected region in
VISUAL mode. The line or region is extended to the next bigger syntactic
entity.

It operates on the current, potentially unsaved buffer and does not create
or save any files. To revert a formatting, just undo.


Emacs Integration
=================

Similar to the integration for :program:`vim`, there is an integration for
:program:`emacs`. It can be found at `clang/tools/clang-format/clang-format.el`
and used by adding this to your `.emacs`:

.. code-block:: common-lisp

  (load "<path-to-clang>/tools/clang-format/clang-format.el")
  (global-set-key [C-M-tab] 'clang-format-region)

This binds the function `clang-format-region` to C-M-tab, which then formats the
current line or selected region.


BBEdit Integration
==================

:program:`clang-format` cannot be used as a text filter with BBEdit, but works
well via a script. The AppleScript to do this integration can be found at
`clang/tools/clang-format/clang-format-bbedit.applescript`; place a copy in
`~/Library/Application Support/BBEdit/Scripts`, and edit the path within it to
point to your local copy of :program:`clang-format`.

With this integration you can select the script from the Script menu and
:program:`clang-format` will format the selection. Note that you can rename the
menu item by renaming the script, and can assign the menu item a keyboard
shortcut in the BBEdit preferences, under Menus & Shortcuts.


Script for patch reformatting
=============================

The python script `clang/tools/clang-format-diff.py` parses the output of
a unified diff and reformats all contained lines with :program:`clang-format`.

.. code-block:: console

  usage: clang-format-diff.py [-h] [-p P] [-style STYLE]

  Reformat changed lines in diff.

  optional arguments:
    -h, --help    show this help message and exit
    -p P          strip the smallest prefix containing P slashes
    -style STYLE  formatting style to apply (LLVM, Google, Chromium, Mozilla,
                  WebKit)

So to reformat all the lines in the latest :program:`git` commit, just do:

.. code-block:: console

  git diff -U0 HEAD^ | clang-format-diff.py -p1

The :option:`-U0` will create a diff without context lines (the script would format
those as well).