flycheck-gcc-include-path in .dir-locals.el

Question

In my .dir-locals.el I have:

(cpp-mode . (setq flycheck-gcc-include-path '("/home/<user>/<project>/include")))

This doesnt seem to set flycheck-gcc-include-path, any ideas why?

Also is there a list option for flycheck-gcc-include-path so I can specify more than one include directory?

Edit: Heres my flycheck stuff in my init.el:

;; syntax checker flycheck
(add-hook 'after-init-hook #'global-flycheck-mode)
; error showing up console
(with-eval-after-load 'flycheck
  (flycheck-pos-tip-mode))
;(setq flycheck-gcc-include-path '("/home/<user>/<project>"))
(setq flycheck-disabled-checkers '(c/c++-clang))
(setq flycheck-enabled-checkers '(c/c++-gcc))

If I uncomment the line for flycheck-gcc-include-path it works. I want this on a project basis so I am trying to set it in .dir-locals.el

Answer 1

I see a few potential issues:

1. I am not familiar with a cpp-mode; I assume you mean c++-mode.
2. The contents of a dir-locals-file should form an alist, i.e. ((mode . vars)) instead of (mode . vars).
3. The cdr of each such mode-vars pair, i.e. the mode-specific settings, should also form an alist: ((mode . ((var . val)))) instead of ((mode . (var . val))).
4. Each variable-value pair results in the cdr (value) being assigned to the car (variable); the form is not evaluated as is. The cdr is only evaluated when the car comprises the special symbol eval.

So, your dir-locals-file should probably read:

((c++-mode . ((flycheck-gcc-include-path . ("/home/<user>/<project>/include")))))

See the following info manual nodes for more information:

• (emacs) Directory Variables
• (elisp) Directory Local Variables

Also is there a list option for flycheck-gcc-include-path so I can specify more than one include directory?

As far as I can tell from the variable's documentation (C-h v flycheck-gcc-include-path RET) it is supposed to be a list of directory paths. If this does not work you should consider reporting it as a bug.