#+TITLE: C/C++ layer

#+TAGS: general|layer|multi-paradigm|programming

[[file:img/ccpp.jpg]]

* Table of Contents                     :TOC_5_gh:noexport:
- [[#description][Description]]
  - [[#features][Features:]]
- [[#install][Install]]
  - [[#layer][Layer]]
  - [[#default-mode-for-header-files][Default mode for header files]]
  - [[#backends][Backends]]
    - [[#rtags][RTags]]
      - [[#external-dependencies][External dependencies]]
      - [[#configuration][Configuration]]
    - [[#cquery--ccls-lsp-backends][cquery / ccls (lsp backends)]]
      - [[#features-1][Features:]]
      - [[#external-dependencies-1][External dependencies]]
        - [[#cquery-server][cquery server]]
        - [[#ccls-server][ccls server]]
      - [[#configuration-1][Configuration]]
        - [[#basic][Basic]]
        - [[#setting-path-to-backend-executable][Setting path to backend executable]]
        - [[#semantic-highlighting][Semantic highlighting]]
        - [[#additional-configuration-options][Additional configuration options]]
        - [[#example-dotspacemacs-configuration-layers-entry][Example dotspacemacs-configuration-layers entry]]
      - [[#completion][Completion]]
      - [[#debugger-dap-integration][Debugger (dap integration)]]
  - [[#clang-configuration][Clang Configuration]]
    - [[#clang-format][clang-format]]
    - [[#company-clang-and-flycheck][Company-clang and flycheck]]
  - [[#enable-google-set-c-style][Enable google-set-c-style]]
  - [[#newlines][Newlines]]
  - [[#projectile-sub-project-adoption][Projectile sub-project adoption]]
- [[#key-bindings][Key bindings]]
  - [[#formatting-clang-format][Formatting (clang-format)]]
  - [[#rtags-1][RTags]]
  - [[#cquery--ccls][cquery / ccls]]
    - [[#backend-language-server][backend (language server)]]
    - [[#goto][goto]]
      - [[#gotohierarchy][goto/hierarchy]]
      - [[#gotomember][goto/member]]
  - [[#debugger][debugger]]

* Description
This layer adds configuration for C/C++ language.

** Features:
- Support syntax checking via flycheck with Clang.
- Support for disassembly of code with [[https://github.com/jart/disaster][disaster]].
- Support code reformatting with [[http://clang.llvm.org/docs/ClangFormat.html][clang-format]].
- Display function or variable definition at the bottom. (when =semantic= layer
  is included)
- Display current function cursor is in at the top. See [[https://github.com/tuhdo/semantic-stickyfunc-enhance][stickyfunc-demos]] for
  demos in some programming languages. (when =semantic= layer is included)
- Support common refactoring with [[https://github.com/tuhdo/semantic-refactor][semantic-refactor]]. See [[https://github.com/tuhdo/semantic-refactor/blob/master/srefactor-demos/demos.org][srefactor-demos]] for
  demonstration of refactoring features. (when =semantic= layer is included)
- Support code navigation via cscope (when =cscope= layer is included) and gtags.
- Support auto-completion (when =auto-completion= layer is included) via
  company-clang (when =c-c++-enable-clang-support= is turned on), or
  company-ycmd (when =ycmd= layer is included).
- Support for [[https://github.com/realgud/realgud][realgud]] debugger.
- Support for [[https://github.com/Andersbakken/rtags][rtags]].
- Support for [[https://github.com/cquery-project/cquery][cquery]] or [[https://github.com/MaskRay/ccls][ccls]] as an lsp backend.

* Install
** Layer
To use this configuration layer, add it to your =~/.spacemacs=. You will need to
add =c-c++= to the existing =dotspacemacs-configuration-layers= list in this
file.

*Note:* [[https://github.com/tuhdo/semantic-refactor][semantic-refactor]] is only available for Emacs 24.4+

** Default mode for header files
By default header files are opened in =c-mode=, you can open them in =c++-mode=
by setting the variable =c-c++-default-mode-for-headers= to =c++-mode=.

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers
                '((c-c++ :variables c-c++-default-mode-for-headers 'c++-mode)))
#+END_SRC

*Note:* To set the variable for a given project, create a directory local
variable at the root of your project. More info on directory local variables
can be found in the [[http://www.gnu.org/software/emacs/manual/html_node/elisp/Directory-Local-Variables.html][dir-locals]].

** Backends
This layer supports the selection of one of 3 available backends for code navigation etc via the =c-c++-backend= configuration variable.

*** RTags
RTags is a well established clang-based source code indexing tool.

**** External dependencies
Install the RTags server via [[https://formulae.brew.sh/formula/rtags][homebrew]], the [[https://aur.archlinux.org/packages/rtags/][aur]] or from source according to the instructions [[https://github.com/Andersbakken/rtags][here]].
N.B. RTags is not supported on Windows at the time of writing, although there is an [[https://github.com/Andersbakken/rtags/issues/770][open issue with some recent activity]] on github.

**** Configuration
To enable support for =rtags=, set the layer variable =c-c++-backend=:

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers
                '((c-c++ :variables c-c++-backend 'rtags)))
#+END_SRC

This will also enable =company-rtags= to be used as a backend for
auto-completion (when =auto-completion= layer is included).
To prevent this, while retaining the rest of Rtags functionality,
set the variable =c-c++-rtags-completion= to =nil=:

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers
                '((c-c++ :variables
                         c-c++-backend 'rtags
                         c-c++-enable-rtags-completion nil)))
#+END_SRC

*** cquery / ccls (lsp backends)
[[https://github.com/cquery-project/cquery][cquery]] and [[https://github.com/MaskRay/ccls][ccls]] are alternative implementations of the language server protocol based on libclang. They claim to be more efficient
than existing tools at indexing large code bases.

**** Features:
- Cross references (definitions, references, base/derived classes/methods, type instances, ...)
- Diagnostics
- Completion with =company-lsp=
- Semantic highlighting
- See more on [[https://github.com/cquery-project/cquery/wiki/Emacs]]
- Cross-platform - functional on Windows, Linux and OSX.

**** External dependencies
Install one (or both) of the following:

***** cquery server
Install the =cquery= server. [[https://github.com/cquery-project/cquery/wiki/Getting-started][Instructions]].

***** ccls server
Install the =ccls= server. [[https://github.com/MaskRay/ccls/wiki/Getting-started][Instructions]].

**** Configuration
***** Basic
Select either =cquery= or =ccls= as the =c-c++= layer backend by adding the following to your dotfile:

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers
                '((c-c++ :variables c-c++-backend 'lsp-cquery))) ;or 'lsp-ccls
#+END_SRC

N.B. The [[file:../../+tools/lsp/README.org][LSP layer]] will be loaded automatically if either backend is selected.

***** Setting path to backend executable
The basic configuration above should work if the cquery/ccls executable folder is present in your path. If not, you can set the path explicitly.

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers
                '((c-c++ :variables
                         c-c++-backend 'lsp-cquery
                         c-c++-lsp-executable "/path/to/bin/cquery/or/ccls")))
#+END_SRC

If you need to expand =~= in the path, you can use =file-truename= like

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers
                '((c-c++ :variables
                         c-c++-backend 'lsp-cquery
                         c-c++-lsp-executable (file-truename "~/bin/cquery/or/ccls"))))
#+END_SRC

***** Semantic highlighting
Semantic highlighting is disabled by default. To enable, set the =c-c++-lsp-sem-highlight-method= variable to either ='font-lock= or ='overlay=.
To enable the rainbow semantic highlighting colour theme, set =c-c++-lsp-sem-highlight-rainbow= to =t=.

***** Additional configuration options
Both lsp backends are configured to store their index cache in a subdirectory of =.emacs.d/cache=. This can be overridden by
specifying an explicit =c-c++-lsp-cache-dir=. Setting this value to a relative path will cause the index cache to be placed in a
subdirectory of your project root.

There are other initialization options such as the number of indexer threads, cache serialization format.
They have good default values. See =config.el= of the layer and the backends' respective homepages for more info.
- [[https://github.com/cquery-project/cquery/wiki/Emacs][Emacs section of =cquery= wiki]]
- [[https://github.com/MaskRay/ccls/wiki/Emacs][Emacs section of =ccls= wiki]]

***** Example dotspacemacs-configuration-layers entry
#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers
                '((c-c++ :variables
                         c-c++-adopt-subprojects t
                         c-c++-backend 'lsp-ccls
                         c-c++-lsp-executable (file-truename "~/dev/cpp/ccls/Release/ccls")
                         c-c++-lsp-sem-highlight-rainbow t)))
#+END_SRC

**** Completion
=company-lsp= provides completion functionality. Client-side cache and sorting have been disabled in favour of server,
as recommended by =cquery=/=ccls= wikis.

**** Debugger (dap integration)
To install the debug adapter you may run =M-x dap-gdb-lldb-setup= when you are on Linux or download it manually from [[https://marketplace.visualstudio.com/items?itemName=webfreak.debug][Native Debug]] and adjust =dap-gdb-lldb-path=.

** Clang Configuration
To enable Clang support, set the layer variable =c-c++-enable-clang-support=
to =t= in the dotfile:

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers
                '((c-c++ :variables c-c++-enable-clang-support t)))
#+END_SRC

N.B. do not set this option if either the =cquery= or =ccls= backend

*** clang-format
[[http://clang.llvm.org/docs/ClangFormat.html][clang-format]] allows reformatting either a selected region of code
(=clang-format-region=) or a whole buffer (=clang-format-buffer=)
according to a style defined in a =.clang-format= file. This file
is either located in the same directory as the file being edited,
or any of its parent directories. If no =.clang-format= is found,
then a default style will be used.

To enable automatic buffer formatting on save, set the variable
=c-c++-enable-clang-format-on-save= to =t=:

#+BEGIN_SRC emacs-lisp
  (setq-default dotspacemacs-configuration-layers
                '((c-c++ :variables c-c++-enable-clang-format-on-save t)))
#+END_SRC

*** Company-clang and flycheck
This layer adds some fancy improvements to =company-clang=. It includes a hook
to load a projects =.clang_complete= file, which is just a text file with one
clang flag per line, a format also used by other text editor clang plugins.

Not only does this allow proper autocomplete on projects with extra includes and
flags, but there is also support for flycheck so that it doesn't complain about
missing header files.

** Enable google-set-c-style
If you have clang enabled with =clang-format= as described earlier in this page
you may not have a lot of neeed for =google-set-c-style= if you are already
using a mode based on Google mode for most of your projects.

However, if you don't have (or want) =clang-format=, or if you have to do a lot
[[https://www.emacswiki.org/emacs/TrampMode][Tramp]] remote editing on systems that don't have =clang-format= installed, you
may want =google-c-style= enabled and added to your common hooks.

To get =google-c-style= actually install itself into your C/C++ common hooks,
you need to have =c-c++-enable-google-style= defined to true when you load the
C-C++ lang in Spacemacs. In your =~/.spacemacs= file, a possible way that this
would look is that in your list of =dostpacemacs-configuration-layers= you have
an entry like

#+BEGIN_SRC emacs-lisp
  (c-c++ :variables c-c++-enable-google-style t)
#+END_SRC

Additionally, if you have =c-c++-enable-google-newline= variable set then
=`google-make-newline-indent= will be set as a =c-mode-common-hook=. You would
set that up like this:

#+BEGIN_SRC emacs-lisp
  (c-c++ :variables c-c++-enable-google-style t
                    c-c++-enable-google-newline t)
#+END_SRC

** Newlines
You can enable the =Auto-newline= minor mode that automatically adds newlines
after certain characters by setting the =c-c++-enable-auto-newline= variable.

#+BEGIN_SRC emacs-lisp
  (c-c++ :variables c-c++-enable-auto-newline t)
#+END_SRC

** Projectile sub-project adoption
To prevent projectile from using subproject root when visiting files in a subproject,
set =c-c++-adopt-subprojects= to =t=.

#+BEGIN_SRC emacs-lisp
  (c-c++ :variables c-c++-adopt-subprojects t)
#+END_SRC

This is based on a recommendation on the =cquery= and =ccls= wikis, but should be more
generally applicable.

* Key bindings

| Key binding | Description                                                   |
|-------------+---------------------------------------------------------------|
| ~SPC m g a~ | open matching file                                            |
|             | (e.g. switch between .cpp and .h, requires a project to work) |
| ~SPC m g A~ | open matching file in another window                          |
|             | (e.g. switch between .cpp and .h, requires a project to work) |
| ~SPC m D~   | disaster: disassemble c/c++ code                              |
| ~SPC m r .~ | srefactor: refactor thing at point.                           |

*Note:* [[https://github.com/tuhdo/semantic-refactor][semantic-refactor]] is only available for Emacs 24.4+.

** Formatting (clang-format)

| Key binding | Description                     |
|-------------+---------------------------------|
| ~SPC m = =~ | format current region or buffer |
| ~SPC m = f~ | format current function         |

** RTags

| Key binding | Description                     |
|-------------+---------------------------------|
| ~SPC m g .~ | find symbol at point            |
| ~SPC m g ,~ | find references at point        |
| ~SPC m g ;~ | find file                       |
| ~SPC m g /~ | find all references at point    |
| ~SPC m g [~ | location stack back             |
| ~SPC m g ]~ | location stack forward          |
| ~SPC m g >~ | c++ tags find symbol            |
| ~SPC m g <~ | c++ tags find references        |
| ~SPC m g B~ | show rtags buffer               |
| ~SPC m g d~ | print dependencies              |
| ~SPC m g D~ | diagnostics                     |
| ~SPC m g e~ | reparse file                    |
| ~SPC m g E~ | preprocess file                 |
| ~SPC m g F~ | fixit                           |
| ~SPC m g G~ | guess function at point         |
| ~SPC m g h~ | print class hierarchy           |
| ~SPC m g I~ | c++ tags imenu                  |
| ~SPC m g L~ | copy and print current location |
| ~SPC m g M~ | symbol info                     |
| ~SPC m g O~ | goto offset                     |
| ~SPC m g p~ | set current project             |
| ~SPC m g R~ | rename symbol                   |
| ~SPC m g s~ | print source arguments          |
| ~SPC m g S~ | display summary                 |
| ~SPC m g T~ | taglist                         |
| ~SPC m g v~ | find virtuals at point          |
| ~SPC m g V~ | print enum value at point       |
| ~SPC m g X~ | fix fixit at point              |
| ~SPC m g Y~ | cycle overlays on screen        |

** cquery / ccls
The key bindings listed below are in addition to the default key bindings defined by the [[file:../../+tools/lsp/README.org][LSP layer]].
A ~[ccls]~ or ~[cquery]~ suffix indicates that the binding is for the indicated backend only.

*** backend (language server)

| Key binding | Description                              |
|-------------+------------------------------------------|
| ~SPC m b f~ | refresh index (e.g. after branch change) |
| ~SPC m b p~ | preprocess file                          |

*** goto

| Key binding | Description               |
|-------------+---------------------------|
| ~SPC m g &~ | find references (address) |
| ~SPC m g R~ | find references (read)    |
| ~SPC m g W~ | find references (write)   |
| ~SPC m g c~ | find callers              |
| ~SPC m g C~ | find callees              |
| ~SPC m g v~ | vars                      |
| ~SPC m g f~ | find file at point (ffap) |
| ~SPC m g F~ | ffap other window         |

**** goto/hierarchy

| Key binding   | Description                 |
|---------------+-----------------------------|
| ~SPC m g h b~ | base class(es)              |
| ~SPC m g h d~ | derived class(es) [ccls]    |
| ~SPC m g h c~ | call hierarchy              |
| ~SPC m g h C~ | call hierarchy (inv)        |
| ~SPC m g h i~ | inheritance hierarchy       |
| ~SPC m g h I~ | inheritance hierarchy (inv) |

**** goto/member

| Key binding   | Description             |
|---------------+-------------------------|
| ~SPC m g m h~ | member hierarchy        |
| ~SPC m g m t~ | member types [ccls]     |
| ~SPC m g m f~ | member functions [ccls] |
| ~SPC m g m v~ | member variables [ccls] |

** debugger

| Key binding   | Description                     |
|---------------+---------------------------------|
| ~SPC m d d d~ | start debugging                 |
| ~SPC m d d l~ | debug last configuration        |
| ~SPC m d d r~ | debug recent configuration      |
|---------------+---------------------------------|
| ~SPC m d c~   | continue                        |
| ~SPC m d i~   | step in                         |
| ~SPC m d o~   | step out                        |
| ~SPC m d s~   | next step                       |
| ~SPC m d v~   | inspect value at point          |
| ~SPC m d r~   | restart frame                   |
|---------------+---------------------------------|
| ~SPC m d .~   | debug transient state           |
|---------------+---------------------------------|
| ~SPC m d a~   | abandon current session         |
| ~SPC m d A~   | abandon all process             |
|---------------+---------------------------------|
| ~SPC m d e e~ | eval                            |
| ~SPC m d e r~ | eval region                     |
| ~SPC m d e t~ | eval value at point             |
|---------------+---------------------------------|
| ~SPC m d S s~ | switch session                  |
| ~SPC m d S t~ | switch thread                   |
| ~SPC m d S f~ | switch frame                    |
|---------------+---------------------------------|
| ~SPC m d I i~ | inspect                         |
| ~SPC m d I r~ | inspect region                  |
| ~SPC m d I t~ | inspect value at point          |
|---------------+---------------------------------|
| ~SPC m d b b~ | toggle a breakpoint             |
| ~SPC m d b c~ | change breakpoint condition     |
| ~SPC m d b l~ | change breakpoint log condition |
| ~SPC m d b h~ | change breakpoint hit count     |
| ~SPC m d b a~ | add a breakpoint                |
| ~SPC m d b d~ | delete a breakpoint             |
| ~SPC m d b D~ | clear all breakpoints           |
|---------------+---------------------------------|
| ~SPC m d '_~  | Run debug REPL                  |
|---------------+---------------------------------|
| ~SPC m d w l~ | list local variables            |
| ~SPC m d w o~ | goto output buffer if present   |
| ~SPC m d w s~ | list sessions                   |
| ~SPC m d w b~ | list breakpoints                |