Re: Emacs design and architecture. How about copy-on-write?

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: yantar92@posteo.net,  emacs-devel@gnu.org
> Date: Thu, 21 Sep 2023 15:34:52 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > I'm not sure I understand: what is the difference between a global
> > variable defined in C and a global variable defined, say, in
> > simple.el?
> 
> The variable defined in C must be accessible by a C lvalue.  Namely,
> 
>   (*current_thread->f_Vname_of_the_variable)

How is this different from

  (setq name-of-variable SOMETHING)

done by some thread to a global variable?