trouble with flycheck-gcc-language-standard variable

Question

I am attempting to use Directory-Variables in order to set the flycheck-gcc-language-standard variable. I used: M-x add-dir-local-variable RET c++-mode RET flycheck-gcc-language-standard RET "c++11" to create the .dir-local.el file in the project root directory. Which results in the following code:

((c++-mode  
  (flycheck-gcc-language-standard . "c++11")))

the above creates a warning that this is a "malformed function". I've tried several variations: without quotes, c++0x instead of c++11, among others. Flycheck.el doesn't list what are acceptable variables. I'm stuck.

Any suggestions would be very much appreciated.

If it helps below is the debugger output:

Debugger entered--Lisp error:
(invalid-function (c++-mode (flycheck-gcc-language-standard . c++11)))
((c++-mode (flycheck-gcc-language-standard . c++11)))
eval(((c++-mode (flycheck-gcc-language-standard . c++11))) nil)
elisp--eval-last-sexp(nil)
eval-last-sexp(nil)
funcall-interactively(eval-last-sexp nil)
call-interactively(eval-last-sexp nil nil)
command-execute(eval-last-sexp)

It seems to me that I'm missing something but I don't know it might be. I new to emacs.

Answer 1

There is nothing wrong here except that flycheck is giving you a bogus warning because it is seeing c++mode as a function. But a dir-locals.el file just holds a specially-constructed list, which maps major mode names (symbols) to alists.

Answer 2

In addition to the explanation by Christopher Gray, you can append the following to your .dir-locals.el files to avoid the spurious warnings.

;; Local Variables: 
;; eval: (flycheck-mode -1) 
;; End: