bug#65267: 30.0.50; modifying debug-ignored-errors during startup with --debug-init is broken

[Štěpán Němec]

sh(1) reproduction recipe:

--8<--
initdir=$(mktemp -d)

echo "(add-to-list 'debug-ignored-errors 'my-error)" >"$initdir"/init.el
emacs --debug-init --init-dir="$initdir" \
      --eval '(message "%S" debug-ignored-errors)'

rm -rf "$initdir"
--8<--

In the emacs thus started, the value of `debug-ignored-errors' is
"(my-error startup--witness)" instead of `my-error' added to
the default ignored error symbol list.

(It works as expected *without* --debug-init.)


In GNU Emacs 30.0.50 (build 3, x86_64-pc-linux-gnu, cairo version
 1.17.8) of 2023-08-13 built on tipi
Repository revision: 6d58007bb05b92d5bafb91631df8fef8d99e6722
                     ^
[that's just 08bf8533bb1d with some unrelated stuff on top, sorry about that]
Repository branch: use
Windowing system distributor 'The X.Org Foundation', version 11.0.12101008
System Description: Arch Linux

Configured using:
 'configure --config-cache --without-x-toolkit'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSYSTEMD LIBXML2 M17N_FLT MODULES NOTIFY INOTIFY
OLDXMENU PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF TREE_SITTER
WEBP X11 XDBE XIM XINPUT2 XPM ZLIB

Important settings:
  value of $LC_MESSAGES: 
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=fcitx
  locale-coding-system: utf-8-unix

Major mode: Help

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  file-name-shadow-mode: t
  isearch-fold-quotes-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  buffer-read-only: 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
sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
cl-extra pp cl-print byte-opt gv bytecomp byte-compile debug backtrace
find-func thingatpt help-fns radix-tree help-mode cl-loaddefs cl-lib 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 touch-screen 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 lcms2 dynamic-setting system-font-setting
font-render-setting cairo xinput2 x multi-tty move-toolbar
make-network-process emacs)

Memory information:
((conses 16 55621 13813) (symbols 48 6384 0) (strings 32 18969 1832)
 (string-bytes 1 511550) (vectors 16 12190)
 (vector-slots 8 168978 11702) (floats 8 45 36) (intervals 56 405 0)
 (buffers 992 12))

-- 
Štěpán