bug#61162: 30.0.50; RET in source files that are being displayed by gud no longer works

[Michael Welsh Duggan]

Create a trivial C program.  Here's a good example:

    int main()
    {
      return 0;
    }

Save it as foo.c, and compile it with debugging:

    gcc -ggdb3 -o foo foo.c

>From emacs -Q, start gdb on foo:

    M-x gud-gdb RET 

In my case, since foo is the only executable in the dir, the command
line for gdb is already set up correctly as:

    gdb --fullname foo

Hit RET.  You should be at the gdb prompt.  Start the program:

    start RET

You should now get another window with foo.c in it for context.  Switch
to that buffer and type RET.

    C-x o
    RET

In my case, I get:

    comint-send-input: Current buffer has no process

This is new and broken behavior.  The expected behavior is that a
newline is inserted in the buffer.


In GNU Emacs 30.0.50 (build 2, x86_64-pc-linux-gnu, X toolkit, cairo
 version 1.16.0) of 2023-01-25 built on miko
Repository revision: 8b87d095acfb23b527f955873a59dd9c13ffc9b4
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12101004
System Description: Debian GNU/Linux bookworm/sid

Configured using:
 'configure --without-toolkit-scroll-bars --with-x-toolkit=lucid
 --with-native-compilation --with-xinput2 'CFLAGS=-Og -ggdb'
 --with-tree-sitter'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES
NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3
THREADS TIFF TREE_SITTER WEBP X11 XAW3D XDBE XIM XINPUT2 XPM LUCID ZLIB

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

Major mode: Group

Minor modes in effect:
  gnus-topic-mode: t
  cursor-sensor-mode: t
  gnus-undo-mode: t
  display-time-mode: t
  magit-wip-initial-backup-mode: t
  magit-wip-before-change-mode: t
  magit-wip-after-apply-mode: t
  magit-wip-after-save-mode: t
  magit-wip-mode: t
  global-git-commit-mode: t
  magit-auto-revert-mode: t
  shell-dirtrack-mode: t
  server-mode: t
  tooltip-mode: t
  global-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
  buffer-read-only: t
  line-number-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
/home/md5i/.config/emacs/elpa/transient-0.3.7/transient hides 
/home/md5i/src/emacs/md5i/lisp/transient

Features:
(shadow emacsbug emacs-news-mode noutline outline pulse
display-line-numbers magit-bookmark bookmark man sieve-mode pcmpl-unix
find-dired jka-compr shortdoc help-fns radix-tree gud goto-addr
mailalias smtpmail canlock generic etags fileloop generator xref
calc-misc calc-alg calc-ext calc-menu calc calc-loaddefs rect calc-macs
vc-hg vc-bzr vc-src vc-sccs vc-svn vc-cvs vc-rcs log-view bug-reference
sh-script smie executable dabbrev grep misearch multi-isearch copyright
time-stamp whitespace tabify vc cmake-mode thingatpt rst magit-extras
dired-aux face-remap vc-git vc-dispatcher flow-fill shr-color color
mm-archive qp mule-util sort gnus-cite mail-extr textsec uni-scripts
idna-mapping ucs-normalize uni-confusable textsec-check gnus-async
gnus-bcklg gnus-ml disp-table gnus-topic cursor-sensor nndraft nnmh
nnfolder utf-7 epa-file network-stream gnus-agent gnus-srvr gnus-score
score-mode nnvirtual gnus-msg gnus-art mm-uu mml2015 mm-view mml-smime
smime dig gnus-cache gnus-sum shr pixel-fill kinsoku url-file svg
gnus-demon nntp gnus-group gnus-undo gnutls gnus-start gnus-dbus
gnus-cloud gnus-spec gnus-win flyspell ispell view pacproxy descr-text
tramp tramp-loaddefs trampver tramp-integration cus-edit pp cus-load
files-x tramp-compat parse-time iso8601 ls-lisp time sieve-manage sasl
sasl-anonymous sasl-login sasl-plain rng-loc rng-uri rng-parse rng-match
rng-dt rng-util rng-pttrn nxml-parse nxml-ns nxml-enc xmltok nxml-util
sgml-mode facemenu dom python project compat pcase treesit ps-print
ps-print-loaddefs lpr picture nm dbus xml magit-submodule magit-obsolete
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 magit-repos
magit-apply magit-wip magit-log which-func imenu magit-diff smerge-mode
diff diff-mode easy-mmode git-commit log-edit pcvs-util add-log
magit-core magit-autorevert autorevert filenotify magit-margin
magit-transient magit-process with-editor shell pcomplete server
magit-mode transient comp comp-cstr warnings icons rx cl-extra edmacro
kmacro help-mode format-spec magit-git magit-section magit-utils crm
dash nnimap nnmail gnus-int mail-source gnus-range message sendmail
yank-media rfc822 mml mml-sec epa mm-decode mm-bodies mm-encode
mailabbrev gmm-utils mailheader utf7 nnoo gnus wid-edit nnheader
gnus-util time-date mail-utils range gnus-o365-oauth2 oauth2 url-http
url-auth mail-parse rfc2231 rfc2047 rfc2045 mm-util ietf-drums
mail-prsvr url-gw nsm puny plstore generated generic-x epg rfc6068
epg-config ediff ediff-merg ediff-mult ediff-wind ediff-diff ediff-help
ediff-init ediff-util dired-x dired dired-loaddefs compile
text-property-search comint ansi-osc ring ansi-color cc-mode cc-fonts
cc-guess cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs
derived magit-autoloads git-commit-autoloads magit-section-autoloads
transient-autoloads with-editor-autoloads debbugs-autoloads
ahg-autoloads flycheck-autoloads pkg-info-autoloads epl-autoloads
js2-mode-autoloads company-autoloads rainbow-delimiters-autoloads info
debian-el package browse-url url url-proxy url-privacy url-expand
url-methods url-history url-cookie generate-lisp-file url-domsuf
url-util mailcap url-handlers url-parse auth-source cl-seq eieio
eieio-core cl-macs password-cache json subr-x map byte-opt gv bytecomp
byte-compile url-vars 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 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 x-toolkit
xinput2 x multi-tty make-network-process native-compile emacs)

Memory information:
((conses 16 2569013 179021)
 (symbols 48 54509 8)
 (strings 32 301965 34664)
 (string-bytes 1 9142322)
 (vectors 16 154479)
 (vector-slots 8 2479637 295788)
 (floats 8 1620 935)
 (intervals 56 113568 607)
 (buffers 984 156))

-- 
Michael Welsh Duggan
(md5i@md5i.com)