bug#69293: 30.0.50; cc-mode doesn't support "if consteval"

[Herman]

C++ has a new feature, "if consteval". So one can write code like

if consteval {
    // do something
} else {
    // do something else
}

The problem is that cc-mode doesn't recognize this construct, lines
are not indented correctly: the "// do something" and the "} else {"
receive an additional level of indentation.


In GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, cairo version
 1.18.0) of 2023-11-29 built on okoska
Repository revision: 47837b3863deba274f16960f1ee9fde4acb9d5a1
Repository branch: my-modifications
Windowing system distributor 'The X.Org Foundation', version 11.0.12101008
System Description: Debian GNU/Linux trixie/sid

Configured using:
 'configure --with-native-compilation --without-compress-install
 --without-gconf --without-gsettings --without-dbus --with-small-ja-dic
 --with-json --with-xinput2 --with-x-toolkit=no --with-tree-sitter
 --with-cairo --with-cairo-xcb --disable-silent-rules
 'CFLAGS=-mtune=native -march=native -g3 -O3''

Configured features:
ACL CAIRO FREETYPE GIF GLIB GMP GNUTLS HARFBUZZ JPEG JSON LCMS2 LIBOTF
LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES NATIVE_COMP 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_ALL: C.UTF-8
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=none
  locale-coding-system: utf-8-unix

Major mode: Fundamental

Minor modes in effect:
  magit-todos-mode: t
  git-identity-magit-mode: t
  global-git-commit-mode: t
  vertico-multiform-mode: t
  recentf-mode: t
  which-key-mode: t
  global-auto-revert-mode: t
  global-undo-tree-mode: t
  undo-tree-mode: t
  savehist-mode: t
  ws-butler-global-mode: t
  ws-butler-mode: t
  diff-hl-flydiff-mode: t
  global-diff-hl-mode: t
  clean-aindent-mode: t
  global-whitespace-mode: t
  projectile-mode: t
  marginalia-mode: t
  vertico-mode: t
  global-anzu-mode: t
  anzu-mode: t
  global-evil-matchit-mode: t
  evil-matchit-mode: t
  evil-snipe-override-mode: t
  evil-snipe-mode: t
  evil-snipe-override-local-mode: t
  evil-snipe-local-mode: t
  global-evil-surround-mode: t
  evil-surround-mode: t
  global-evil-visualstar-mode: t
  evil-visualstar-mode: t
  better-jumper-mode: t
  better-jumper-local-mode: t
  evil-leader-mode: t
  global-evil-leader-mode: t
  global-hl-todo-mode: t
  winum-mode: t
  hes-mode: t
  gcmh-mode: t
  global-page-break-lines-mode: t
  evil-mode: t
  evil-local-mode: t
  save-place-mode: t
  override-global-mode: t
  minibuffer-depth-indicate-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tab-bar-history-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  minibuffer-regexp-mode: t
  column-number-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
  abbrev-mode: t

Load-path shadows:
/home/geza/.emacs.d/elpa/transient-20240201.1100/transient hides 
/usr/local/share/emacs/30.0.50/lisp/transient
~/.emacs.d/lisp/emacs-gdb/gdb-mi hides 
/usr/local/share/emacs/30.0.50/lisp/progmodes/gdb-mi

Features:
(shadow sort mail-extr evil-collection-magit evil-collection-forge
forge-list forge-commands forge-semi forge-bitbucket buck forge-gogs
gogs forge-gitea gtea forge-gitlab glab forge-github ghub-graphql treepy
gsexp ghub url-http url-gw nsm url-auth let-alist gnutls forge-notify
forge-revnote forge-pullreq forge-issue forge-topic yaml parse-time
iso8601 bug-reference forge-post markdown-mode edit-indirect color
noutline outline forge-repo forge forge-core forge-db closql
emacsql-sqlite-common emacsql emacsql-compiler eieio-base magit-todos
pcre2el rxt re-builder async magit-tbdiff git-identity vdiff-magit
magit-ediff ediff ediff-merg ediff-mult ediff-wind ediff-diff ediff-help
ediff-init ediff-util vdiff magit-bookmark magit-autoloads
magit-submodule magit-blame magit-stash magit-reflog magit-bisect
magit-push magit-pull magit-fetch magit-clone magit-remote magit-commit
magit-sequence magit-notes magit-worktree magit-tag magit-merge
magit-branch magit-reset magit-files magit-refs magit-status magit
package browse-url url url-proxy url-privacy url-expand url-methods
url-history url-cookie generate-lisp-file url-domsuf url-util
url-handlers url-parse auth-source json map url-vars magit-repos
magit-apply magit-wip magit-log which-func imenu magit-diff hydra lv
smerge-mode git-commit log-edit add-log magit-core magit-autorevert
magit-margin magit-transient magit-process with-editor shell pcomplete
server magit-mode transient magit-git magit-base magit-section
format-spec crm emacsbug message mailcap yank-media puny
evil-collection-dired dired-git-info peep-dired dired-narrow delsel
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evil-collection-wdired wdired ls-lisp dired dired-loaddefs rfc822 mml
mml-sec password-cache epa derived epg rfc6068 epg-config gnus-util
time-date mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev
gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util
mail-prsvr mail-utils mule-util cursor-sensor evil-collection-consult
consult-dir vertico-multiform consult-compile recentf tree-widget
wid-edit shut-up consult bookmark pp face-remap drag-stuff which-key
autorevert filenotify undo-tree queue savehist bm evil-collection-info
info ws-butler diff-hl-flydiff diff diff-hl log-view pcvs-util vc-dir
ewoc vc vc-dispatcher diff-mode clean-aindent-mode column-enforce-mode
whitespace projectile project lisp-mnt evil-collection-wgrep wgrep
evil-collection-grep grep compile text-property-search
evil-collection-comint comint ansi-osc ansi-color ibuf-ext ibuffer
ibuffer-loaddefs orderless marginalia vertico anzu evil-matchit
evil-matchit-evil-setup evil-matchit-sdk semantic/lex semantic/fw eieio
eieio-core mode-local find-func evil-exchange evil-args evil-indent-plus
evil-textobj-line evil-textobj-entire evil-textobj-column
evil-textobj-anyblock evil-snipe evil-surround evil-mc
evil-mc-command-execute evil-mc-command-record evil-mc-cursor-make
evil-mc-region evil-mc-cursor-state evil-mc-undo evil-mc-vars
evil-mc-known-commands evil-mc-common avy evil-visualstar
evil-collection-simple evil-collection-replace evil-collection annalist
better-jumper pcase cl-macs evil-leader hl-todo compat hl-line
transpose-frame winum dash ov highlight-escape-sequences gcmh
page-break-lines evil evil-integration evil-maps evil-commands reveal
evil-jumps evil-command-window evil-types evil-search evil-ex
evil-macros evil-repeat evil-states evil-core evil-common thingatpt rect
evil-vars ring edmacro kmacro byte-opt saveplace bind-key easy-mmode
advice mb-depth comp cl-seq comp-cstr cl-extra help-mode warnings icons
subr-x gv cl-loaddefs cl-lib bytecomp byte-compile comp-run comp-common
rx jka-compr 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 inotify lcms2 dynamic-setting font-render-setting cairo xinput2
x multi-tty move-toolbar make-network-process native-compile emacs)

Memory information:
((conses 16 618221 566082) (symbols 48 34440 269)
 (strings 32 284048 52426) (string-bytes 1 13838690)
 (vectors 16 75118) (vector-slots 8 1319006 1056891)
 (floats 8 400 2175) (intervals 56 912 295) (buffers 992 12))