Re: Confused by y-or-n-p

[Eli Zaretskii]

> From: Tassilo Horn <tsdh@gnu.org>
> Cc: emacs-devel@gnu.org
> Date: Wed, 06 Jan 2021 17:36:49 +0100
> 
> > But did installing foobar-8.1.0 remove the installation of
> > foobar-7.1.0?
> 
> Yes.  Indeed the emacs package (on my Arch install) installs both
> /usr/bin/emacs and /usr/bin/emacs-27.1 so it could keep the old version
> of the binary around, and also the lisp in /usr/share/emacs/27.1/.  But
> then the question is when and how are those files eventually going to be
> removed?

When the user decides to do so, possibly never.  E.g., I keep old
versions of all the main programs I use: Emacs, GCC, GDB, and some
others.  It is handy to have when the last version turns out to have
some grave bug, or when I want to know which version introduced some
new feature or some exciting bug.  Disk space is cheap nowadays,
whereas my time is all but cheap.

> And what about the files in /usr/share/emacs/site-lisp/?  If
> they were byte-compiled with the newer version, is there a guarantee
> they'll work in all the older versions?

Yes, we seldom if ever break backward compatibility, precisely so
site-lisp doesn't need to be recompiled.  (There's a versioned
site-lisp subdirectory under /usr/share/emacs/XY.Z as well, for the
packages that do depend on Emacs version.)

> > Do distros forcibly remove those versioned files and directories when
> > they install a new version?
> 
> Yes, as said.

Too bad.

Thanks for the info.