Re: Arbitrary function: find the number(s) of expected arguments

[Eli Zaretskii]

> Date: Sat, 19 Mar 2016 13:26:47 +0100
> From: Paul Pogonyshev <address@hidden>
> Cc: address@hidden
> 
> What if I use `subr-arity' for whatever reason in a case where it works, but 
> in the next version Emacs moves
> the function from `.c' to `.el' and it ceases to be a built-in?

You need to guard the calls to subr-arity with subrp, and then your
code will be future-proof.

Patches to add func-arity to Emacs are welcome.