Added emacs libopencm3 auto completion write-up

content/post/emacs_clang_libopencm3.md

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