> Please note that when the search string is too long for char folding,
> then it displays the message at the end of the Isearch prompt
> before disabling char folding:

Emacs doesn’t display any message, I’ve tried catching it with
‘(setq debug-on-message "Too")’ but got nothing.

> But the regexp have limitations when matching runs out of
> internal stack space.  This is described in the Info node:
>   (info "(elisp) Regexp Problems")

I’ve found the Info node on [1] but not in my Emacs nor on [2].
Could it be that both the node and the message are new features of
versions > 27.2?

1
https://github.com/emacs-mirror/emacs/blob/master/doc/lispref/elisp.texi#L1322
2
https://www.gnu.org/software/emacs/manual/html_node/elisp/Regular-Expressions.html

Thanks,
Andrea