bug#70784: Abolish string resizing

[Eli Zaretskii <eliz@gnu.org>]

> From: Po Lu <luangruo@yahoo.com>
> Cc: Drew Adams <drew.adams@oracle.com>,  mattias.engdegard@gmail.com,
>   70784@debbugs.gnu.org,  monnier@iro.umontreal.ca
> Date: Mon, 06 May 2024 20:29:05 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Which is why no one is proposing to make string immutable.  This is
> > not what this proposal is about, and Mattias made a point of saying
> > that explicitly.
> 
> The point is that CL string implementations are capable of modifying
> strings in such a manner as Mattias proposes to "abolish".  I presume
> some are implemented as Emacs's are, while others simply use a
> representation for multibyte strings where all characters are the same
> wide size (which incidentally there's nothing preventing Emacs from
> implementing).

That doesn't really matter.  "Other applications" do things that Emacs
doesn't necessarily want to do, or vice versa.  E.g., consider our
support for raw bytes in multibyte strings, which is quite unique.

What _would_ matter is if there are important use cases out there
where replacing one character by another character of a different
multibyte length.  So if you, or anyone else, can come up with such
situations (which are not made up specifically to argue here), please
do, because knowing about such situations would be useful to make this
discussion serious and based on facts.