c-lang-const is a Lisp macro in `cc-defs.el'.

(c-lang-const NAME &optional LANG)

Get the mode specific value of the language constant NAME in language LANG.
LANG is the name of the language, i.e. the mode name without the
"-mode" suffix. If used inside `c-lang-defconst' or
`c-lang-defvar', LANG may be left out to refer to the current
language. NAME and LANG are not evaluated so they should not be