Re: native-comp write path?

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Yuri D'Elia <wavexx@thregr.org>,  emacs-devel@gnu.org
> Date: Sat, 12 Feb 2022 12:59:08 -0500
> 
> >> I'd like to move the directory inside the XDG_CACHE hierarchy
> > IMO, this is a mistake: the eln-cache is supposed to be more
> > persistent than XDG_CACHE, and even more than the entire XDG
> > hierarchy.  It isn't really a "cache" in the XDG sense.
> 
> Really?  I thought the main defining feature of "cache" is that any of
> those files can be thrown away an the system will work as well (tho
> potentially a bit less efficiently) and the files will/can be
> transparently re-generated if/when needed.
> 
> The files in eln-cache seem to fit the description.

The *.eln files don't need to be updated as long as you don't modify
the corresponding *.el files.  This means that, for an Emacs built and
installed using the default procedure, the eln-cache will quickly fill
up with compiled *.el files from the Emacs distribution that you
frequently use.  If those *.eln files are removed, Emacs will
recompile them upon next startup, which might take a few minutes
during which Emacs will be more sluggish than usually (because JIT
native compilation by default uses half of the system's execution
units).

If you don't care about this, maybe it's okay to move the *.eln files
to the XDG cache.  But you need to understand the affects of this.

> Or is XDG's cache not expected to survive a login session?

I think it can disappear when you log off.  Which is also something to
keep in mind: your Emacs will compile the same files time and again
each login.