spacemacs/layers/+lang/c-c++/funcs.el

;;; funcs.el --- C/C++ Layer functions File for Spacemacs
;;
;; Copyright (c) 2012-2017 Sylvain Benner & Contributors
;;
;; Author: Sylvain Benner <sylvain.benner@gmail.com>
;; URL: https://github.com/syl20bnr/spacemacs
;;
;; This file is not part of GNU Emacs.
;;
;;; License: GPLv3

(defun company-mode/more-than-prefix-guesser ()
  (c-c++/load-clang-args)
  (company-clang-guess-prefix))

;; Based on the Sarcasm/irony-mode compilation database code.
(defun company-mode/find-clang-complete-file ()
  (when buffer-file-name
    (let ((dir (locate-dominating-file buffer-file-name ".clang_complete")))
      (when dir
        (concat (file-name-as-directory dir) ".clang_complete")))))

;; Based on the Sarcasm/irony-mode compilation database code.
(defun company-mode/load-clang-complete-file (cc-file)
  "Load the flags from CC-FILE, one flag per line."
  (let ((invocation-dir (expand-file-name (file-name-directory cc-file)))
        (case-fold-search nil)
        compile-flags)
    (with-temp-buffer
      (insert-file-contents cc-file)
      ;; Replace relative paths with absolute paths (by @trishume)
      ;; (goto-char (point-min))
      (while (re-search-forward "\\(-I\\|-isystem\n\\)\\(\\S-+\\)" nil t)
        (replace-match (format "%s%s" (match-string 1)
                               (expand-file-name (match-string 2) invocation-dir))))
      ;; Turn lines into a list
      (setq compile-flags
            ;; remove whitespaces at the end of each line, if any
            (mapcar #'(lambda (line)
                        (if (string-match "[ \t]+$" line)
                            (replace-match "" t t line)
                          line))
                    (split-string (buffer-string) "\n" t))))
    compile-flags))

(defun c-c++/load-clang-args ()
  "Sets the arguments for company-clang, the system paths for company-c-headers
and the arguments for flyckeck-clang based on a project-specific text file."
  (unless company-clang-arguments
    (let* ((cc-file (company-mode/find-clang-complete-file))
           (flags (if cc-file (company-mode/load-clang-complete-file cc-file) '()))
           (dirs (mapcar (lambda (f) (substring f 2))
                         (remove-if-not (lambda (f) (string-prefix-p "-I" f)) flags))))
      (setq-local company-clang-arguments flags)
      (setq-local company-c-headers-path-system (append '("/usr/include" "/usr/local/include") dirs))
      (setq-local flycheck-clang-args flags))))