This is how you check if an object is a built-in function:
(subrp (symbol-function 'assoc))
=> t
Is there an equivalent way to do this for variables as well?
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I suppose `(help-C-file-name SUBR-OR-VAR KIND)` is the best we've got – John DeBord Aug 25 '21 at 22:52
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I assume that by "built-in" you mean a variable defined in C. This should do it:
(defun built-in-var-p (variable)
"Return non-nil if VARIABLE is defined in C source code."
(let ((file-name (find-lisp-object-file-name variable 'defvar)))
(and file-name (eq file-name 'C-source))))
Drew
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Internally, `find-lisp-object-file-name` calls `help-C-file-name`. Is there a reason to prefer one over the other? – John DeBord Aug 26 '21 at 02:50
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@JohnDeBord: No, not that I know of. I basically took this code from `describe-variable` etc. in `help-fns.el`. Please consider adding your comment that suggests `help-C-file-name` as an answer! Thx. – Drew Aug 26 '21 at 18:05