bug#18577: Regexp I-search: [(error Stack overflow in regexp matcher)]

[Stefan Kangas]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Stefan Kangas <stefan@marxist.se>
>> Date: Fri, 22 Oct 2021 19:47:53 -0700
>> Cc: Alan Mackenzie <acm@muc.de>, Andreas Schwab <schwab@linux-m68k.org>,
>>  18577@debbugs.gnu.org
>>
>> Should we do anything about this, like document it in etc/PROBLEMS, or
>> should this bug just be closed?
>
> If we can give useful advice in PROBLEMS, adding that can never hurt.

Perhaps we could just say this (which makes it easy to search for as the
headline matches the error message):

diff --git a/etc/PROBLEMS b/etc/PROBLEMS
index ede83a6e7c..1b10e20272 100644
--- a/etc/PROBLEMS
+++ b/etc/PROBLEMS
@@ -742,6 +742,15 @@ completed" message that tls.el relies upon,
causing affected Emacs
 functions to hang.  To work around the problem, use older or newer
 versions of gnutls-cli, or use Emacs's built-in gnutls support.

+*** Stack overflow in regexp matcher.
+Due to fundamental limitations in the way Emacs' regular expression
+engine is designed, you might run into combinatorial explosions in
+backtracking with certain regexps.
+
+See Emacs Bug#18577 for a discussion and ideas for how to solve it:
+
+    https://debbugs.gnu.org/18557
+
 * Runtime problems related to font handling

 ** Characters are displayed as empty boxes or with wrong font under X.