130 lines
3.6 KiB
Markdown
130 lines
3.6 KiB
Markdown
---
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title: "Auto-complete for libopencm3 in Emacs"
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date: 2019-10-18
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lastmod: 2019-10-18
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tags: ["emacs", "linux"]
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categories: ["Tutorial"]
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contentCopyright: true
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hideHeaderAndFooter: false
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cover:
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image: /static/img/emacs-clang-libopencm3/header-completion.png
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---
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With some minor dependencies, it's fairly straightforward in setting up your
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Emacs workflow to include IntelliSense-like auto-completion!
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<!--more-->
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{{< img src="/static/img/emacs-clang-libopencm3/header-completion.png"
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sub="Header Completion"
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alt="Screenshot showing auto-completion for C header files in emacs" >}}
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# Dependencies
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## System
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Assuming you're running Linux, you'll need to have the following packages
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installed:
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- `cmake`
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- `libclang`
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## Emacs
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### ELPA
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If you already have ELPA/MELPA, feel free to skip this first part
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To be able to easily fetch the packages, it's highly recommended you use the
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**Emacs Lisp Package Archive** (ELPA). To do this, all that's required is to
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simply add the following to your `init.el`/`.emacs`[^1] file:
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```lisp
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(require 'package)
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(add-to-list 'package-archives
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'("melpa" . "https://melpa.org/packages/"))
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(package-initialize)
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```
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{{< sub >}}
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Emacs will need to be restarted or reloaded to load the package
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repository.
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{{< /sub >}}
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### Packages
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Install the following packages in Emacs (`M-x package-install`):
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- `irony`
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- `company`
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- `company-irony`
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- `company-irony-c-headers` _Required if you want header auto-completion_
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# Configuration
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## Company
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Company ([company-mode](http://company-mode.github.io/)) needs to be required,
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added to the `after-init-hook` (_or similar / manually called_), and the back ends
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to be added to it's list of usable back ends. This is done in the initialization
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file[^1]:
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```lisp
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(require 'company)
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(add-hook 'after-init-hook 'global-company-mode)
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(add-to-list 'company-backends '(company-irony-c-headers company-irony))
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```
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## Irony
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Initial setup of `irony` **requires** `M-x irony-install-server` to be run. If
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errors are encountered, please ensure that you have the necessary [system
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dependencies](https://github.com/Sarcasm/irony-mode#dependencies) installed.
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Irony's `irony-mode` should be added to the relevant C/C++ mode hooks:
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```lisp
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(add-hook 'c++-mode-hook 'irony-mode)
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(add-hook 'c-mode-hook 'irony-mode)
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(add-hook 'objc-mode-hook 'irony-mode)
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```
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Additionally, it's a good idea to add the compile options auto setup helper
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command to the `irony-mode` hook:
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```lisp
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(add-hook 'irony-mode-hook 'irony-cdb-autosetup-compile-options)
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```
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# Usage
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There are several ways to make `irony-mode` aware of what it should look for in
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it's completion. My preferred method, though not the only one, is to simply add
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my compile flags in the special `.clang_complete` file as part of the working
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directory of the project.
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For an STM32F0 project, the context of the `.clang_complete` file would be:
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```text
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-I./libopencm3/include
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-DSTM32F0
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```
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{{< sub >}}
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The above assumes that `libopencm3` is also places within the project
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directory
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{{< /sub >}}
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There is a strange issue that is encountered with non-working completion for new
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header include statements. The workaround for this includes running `M-x irony-server-kill`after new header
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additions to your current working file. Irony's server is clever enough to
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restart itself after a completion request is triggered via `TAB` so this is a
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fairly uninvolved workaround.
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## Example
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{{< img src="/static/img/emacs-clang-libopencm3/completion.png"
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sub="Completion"
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alt= "Screenshot showing auto completion for C functions in emacs">}}
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[^1]: [Emacs Initialization File](https://www.gnu.org/software/emacs/manual/html_node/emacs/Init-File.html)
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