Hi Clang developers,
I’ve seen that there is a Clang-based completion plugin for Emacs in utils/clang-completion-mode.el. However, that library appears unmaintained (last change was more than four years ago) and not widely used (I’ve found only one old blog post - https://kristianrumberg.wordpress.com/2010/04/22/smart-autocompletion-for-c-in-emacs/ - about it on the web). Also it doesn’t use any of the standard completion frontends (company, auto-complete), but massively changes keyboard input (e.g. rebinds almost all normal keys). The initial revision was described as “Experimental, ultra-hacking” and I wouldn’t say the code quality has improved much since then (e.g. it uses very short variable names for global variables, even though Elisp doesn’t have namespaces). Furthermore, when I tried to use clang-completion-mode.el, I wasn’t able to get it working at all, but it nevertheless disturbs editing massively (e.g. no longer allowing the user to enter a space). On the other hand, there are now multiple well-maintained Clang-based completion frameworks (https://github.com/abingham/emacs-ycmd, https://github.com/brianjcj/auto-complete-clang) available that don’t suffer from any of these problems. Overall I’d suggest to remove clang-completion-mode.el.