With emacs -Q load the attached file elinfo.el. Now type C-h S split-window RET C-x o C-c C-g This crashes Emacs here with Thread 1 "emacs" received signal SIGSEGV, Segmentation fault. 0x000000000068810a in skip_noops (p=, pend=) at ../../src/regex-emacs.c:3556 3556 { and an infinite backtrace starting with Python Exception Cannot access memory at address 0x7fffff66fff8: #0 0x000000000068810a in skip_noops (p=#1 0x0000000000688823 in mutually_exclusive_p (bufp=0xec9c30 , p1=0x1fcee74 "\004\005", p2=0x1fcee81 "\016\063") at ../../src/regex-emacs.c:3665 #2 0x0000000000688e19 in mutually_exclusive_p (bufp=0xec9c30 , p1=0x1fcee74 "\004\005", p2=0x1fcee81 "\016\063") at ../../src/regex-emacs.c:3838 #3 0x0000000000688e3c in mutually_exclusive_p (bufp=0xec9c30 , p1=0x1fcee74 "\004\005", p2=0x1fceeba "\004\020") at ../../src/regex-emacs.c:3839 #4 0x0000000000688e3c in mutually_exclusive_p (bufp=0xec9c30 , p1=0x1fcee74 "\004\005", p2=0x1fcee84 "\002\001@\004\020") at ../../src/regex-emacs.c:3839 #5 0x0000000000688e19 in mutually_exclusive_p (bufp=0xec9c30 , p1=0x1fcee74 "\004\005", p2=0x1fcee81 "\016\063") at ../../src/regex-emacs.c:3838 ... The same scenario worked well with Emacs 22 through 28. martin In GNU Emacs 29.1.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.5, cairo version 1.16.0) of 2023-09-03 built on restno Repository revision: f1e4cbe72aa4da9351cbbcd209d9233c68dd9fbb Repository branch: emacs-29 Windowing system distributor 'The X.Org Foundation', version 11.0.12004000 System Description: Debian GNU/Linux 10 (buster) Configured using: 'configure --with-gif=ifavailable --with-tiff=ifavailable --with-gnutls=no --without-pop --enable-gcc-warnings=warn-only --enable-checking=yes,glyphs --enable-check-lisp-object-type=yes 'CFLAGS=-O0 -g3 -no-pie -Wno-missing-braces'' Configured features: CAIRO DBUS FREETYPE GIF GLIB GSETTINGS HARFBUZZ JPEG LIBSELINUX MODULES NOTIFY INOTIFY PDUMPER PNG SECCOMP SOUND THREADS TOOLKIT_SCROLL_BARS X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB Important settings: value of $LANG: de_AT.utf8 value of $XMODIFIERS: @im=ibus locale-coding-system: utf-8-unix Major mode: Lisp Interaction Minor modes in effect: tooltip-mode: t global-eldoc-mode: t eldoc-mode: t show-paren-mode: t electric-indent-mode: t mouse-wheel-mode: t tool-bar-mode: t menu-bar-mode: t file-name-shadow-mode: t global-font-lock-mode: t font-lock-mode: t blink-cursor-mode: t line-number-mode: t indent-tabs-mode: t transient-mark-mode: t auto-composition-mode: t auto-encryption-mode: t auto-compression-mode: t Load-path shadows: None found. Features: (shadow sort mail-extr emacsbug message mailcap yank-media puny dired dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg rfc6068 epg-config gnus-util text-property-search time-date subr-x mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader cl-loaddefs cl-lib sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils elinfo texinfo texinfo-loaddefs info rmc iso-transl tooltip cconv eldoc paren electric uniquify ediff-hook vc-hooks lisp-float-type elisp-mode mwheel term/x-win x-win term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe tabulated-list replace newcomment text-mode lisp-mode prog-mode register page tab-bar menu-bar rfn-eshadow isearch easymenu timer select scroll-bar mouse jit-lock font-lock syntax font-core term/tty-colors frame minibuffer nadvice seq simple cl-generic indonesian philippine cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech european ethiopic indian cyrillic chinese composite emoji-zwj charscript charprop case-table epa-hook jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button loaddefs theme-loaddefs faces cus-face macroexp files window text-properties overlay sha1 md5 base64 format env code-pages mule custom widget keymap hashtable-print-readable backquote threads dbusbind inotify dynamic-setting system-font-setting font-render-setting cairo move-toolbar gtk x-toolkit xinput2 x multi-tty make-network-process emacs) Memory information: ((conses 16 45758 8352) (symbols 48 5682 0) (strings 32 15622 2110) (string-bytes 1 431024) (vectors 16 10081) (vector-slots 8 157669 13073) (floats 8 26 23) (intervals 56 218 0) (buffers 976 10))