bug#81445: 30.2; Crash with Nonspacing Mark

> From: Stefan Monnier <[email protected]>
> Cc: [email protected],  [email protected]
> Date: Mon, 03 Aug 2026 17:47:34 -0400
> 
> >> So maybe a better option is to specbind
> >> `Vload_source_file_function` to nil so we'd also avoid the overhead
> >> of going through `load-with-code-conversion` for those files, where's
> >> it's just a waste, AFAICT, and has a non-negligible performance impact.
> >> 
> >> [ I'm also favorable to removing the `no-byte-compile:t` from those
> >>   files unless the corresponding `.elc` is really worse.  ]
> >
> > I feel that the change I suggest above is more conservative and local,
> > thus safer.  After all, this code has been working for us since at
> > least Emacs 25, with no problems, until this semi-crazy use case came
> > along.
> 
> Now that we have the safe fix in `emacs-31`, what do you think
> about applying the below to `master`?

The fix was installed on master, not on emacs-31.  That's because
working around this is very easy, and OTOH I hesitate to make such
low-level changes so close to the release.

Accordingly, I'd wait with the change you propose, at least until some
time passes and no one reports any problems.

I'm also bothered by the fact that the patch silently and a bit
unexpectedly disallows uni-*.el files encoded in some non-trivial
encoding, if we ever need that.  Not sure if this subtlety, which no
one will remember after enough time passes, is worth the minor
performance gain in loading files that are loaded at most once per
session.