Why `read-buffer` is implemented in C?

Why `read-buffer` is implemented in C?

[Óscar Fuentes]

While diagnosing a problem, I stumbled on read-buffer. Why is it
implemented in C? I mean, why is it *still* implemented in C? From my
beginner level of Emacs C-fu, I see nothing there that can't be done in
Elisp.

Re: Why `read-buffer` is implemented in C?

[Eli Zaretskii]

> From: Óscar Fuentes <ofv@wanadoo.es>
> Date: Sun, 05 May 2024 17:38:29 +0200
> 
> While diagnosing a problem, I stumbled on read-buffer. Why is it
> implemented in C? I mean, why is it *still* implemented in C?

Because we didn't have a good enough reason to move it to Lisp.  Such
moves are not really trivial; for starters, you need to make sure that
its Lisp definition will be loaded in loadup before the first Lisp
file that uses read-buffer.  And that's just the tip of the iceberg
(e.g., I see 2 places in C that call read-buffer, so we'd need to make
sure these two places are not used before the Lisp definition is
loaded; etc. etc.).

So we only do such things when we have a good reason, whose advantages
can justify the potential trouble such changes can (and do) cause.
Otherwise, it's simply un-economical.