have gdbmacs start up Emacs rather than attach to it

Additionally, either re-use or kill the GUD interaction buffer rather than
calling `gdb-reset' ourselves: killing it is the documented way to reset.

2 files changed, 141 insertions, 35 deletions

diff --git a/.emacs.d/init.el b/.emacs.d/init.el
index e66dd3ad..2b955f63 100644
--- a/.emacs.d/init.el
+++ b/.emacs.d/init.el
@@ -2274,40 +2274,72 @@ Called by '~/src/dotfiles/bin/emacsclient --spw/update-environment'."
 	(let ((slime-dispatching-connection connection))
 	  (slime-eval cl-form))))))
 
-(defvar-local spw/gdbmacs-target-emacs nil)
-
-(defun spw/gdbmacs-attach (pid)
-  (interactive "nEmacs PID: ")
-  (when-let ((proc (and (boundp 'gud-comint-buffer)
-			(get-buffer-process gud-comint-buffer))))
-    (if (string= gdb-inferior-status "signal-received")
-	;; Avoid wiping out useful info.
-	(error "Possibly Emacs just crashed; not attaching for now")
-      (set-process-query-on-exit-flag proc nil)
-      (kill-buffer gud-comint-buffer)))
-  (require 'gdb-mi)
-  (let ((default-directory (expand-file-name "~/src/emacs/")))
-    (gdb-reset)
-    (gdb (format "gdb -i=mi --pid=%d src/emacs" pid))
-    (setq spw/gdbmacs-target-emacs pid)
-    (gud-basic-call "continue")))
-
-(defun spw/remote-gdbmacs-attach ()
-  (interactive)
-  (call-process "emacsclient" nil "*gdbmacs-emacsclient*" nil
-		"--socket-name=gdbmacs" "--spw/installed"
-		"-e" (prin1-to-string `(spw/gdbmacs-attach ,(emacs-pid)))))
-
-(defun spw/maybe-remote-gdbmacs-attach ()
-  (when (and (eq (daemonp) t)
-	     (file-in-directory-p invocation-directory "~/src/emacs/"))
-    (spw/remote-gdbmacs-attach)))
-(add-hook 'after-init-hook #'spw/maybe-remote-gdbmacs-attach)
+(defun spw/daemon-pid (&optional name)
+  ;; We don't use `server-eval-at' because perhaps we are trying to attach gdb
+  ;; to a wedged Emacs.
+  (let ((socket (file-name-concat server-socket-dir (or name "server"))))
+    (and (file-exists-p socket)
+	 (and-let* ((output (car (process-lines "ss" "-Hplx" "src" socket))))
+	   (and (string-match "pid=\\([[:digit:]]+\\)" output)
+		(string-to-number (match-string 1 output)))))))
+
+(defvar-local spw/gdbmacs-target-pid nil)
+(defvar-local spw/gdbmacs-target-name nil)
+
+(defun spw/gdbmacs-attach (&optional name)
+  (let (pid
+	(arg (if name (concat "--fg-daemon=" name) "--fg-daemon"))
+	(proc (and (boundp 'gud-comint-buffer)
+		   (get-buffer-process gud-comint-buffer))))
+    (when (and proc (string= gdb-inferior-status "signal-received"))
+      ;; Avoid wiping out useful info.
+      (error "Possibly Emacs just crashed; not attaching for now"))
+    (require 'gdb-mi)
+    (cl-flet ((run-or-continue ()
+		(gdb-wait-for-pending
+		 (lambda ()
+		   (with-current-buffer gud-comint-buffer
+		     (setq spw/gdbmacs-target-pid pid
+			   spw/gdbmacs-target-name name))
+		   (if pid
+		       (gud-basic-call "continue")
+		     (gud-basic-call "set cwd ~")
+		     (gdb-wait-for-pending
+		      (lambda () (gud-basic-call "run"))))))))
+      (gdb-wait-for-pending
+       (if (and proc
+		;; Check it looks safe to re-use existing gdb process.
+		(string-prefix-p "exited" gdb-inferior-status)
+		(file-in-directory-p
+		 (buffer-local-value 'default-directory gud-comint-buffer)
+		 (expand-file-name "~/src/emacs/")))
+	   (lambda ()
+	     (gud-basic-call (if (setq pid (spw/daemon-pid name))
+				 (format "attach %d" pid)
+			       (format "set args %s" arg)))
+	     (run-or-continue))
+	 ;; Start up a new process.
+	 (lambda ()
+	   (when (buffer-live-p gud-comint-buffer)
+	     (when proc (set-process-query-on-exit-flag proc nil))
+	     (kill-buffer gud-comint-buffer))
+	   (gdb-wait-for-pending
+	    (lambda ()
+	      (let ((default-directory (expand-file-name "~/src/emacs/")))
+		(gdb (if (setq pid (spw/daemon-pid name))
+			 (format "gdb -i=mi --pid=%d src/emacs" pid)
+		       (format "gdb -i=mi --args src/emacs %s" arg))))
+	      (run-or-continue)))))))))
 
 ;; C-c C-z to attempt to return control to the debugger.
+;;
+;; In the --fg-daemon case, AIUI we are here working around this:
+;;     <https://lwn.net/Articles/909496/>.
 (defun spw/comint-stop-subjob (orig-fun)
-  (if spw/gdbmacs-target-emacs
-      (signal-process spw/gdbmacs-target-emacs 'SIGTSTP)
+  (if-let ((pid (or spw/gdbmacs-target-pid
+		    (setq spw/gdbmacs-target-pid
+			  (spw/daemon-pid spw/gdbmacs-target-name)))))
+      (signal-process pid 'SIGTSTP)
     (funcall orig-fun)))
 (advice-add 'comint-stop-subjob :around #'spw/comint-stop-subjob)
 
diff --git a/bin/emacsclient b/bin/emacsclient
index fe08427d..920c0102 100755
--- a/bin/emacsclient
+++ b/bin/emacsclient
@@ -24,8 +24,11 @@ min_arg=0
 may_start=true
 want_update=false
 want_installed=false
+want_eval=false
+want_version=false
 devel_running=false
 installed_running=false
+pass_to_gdbmacs=false
 socket_dir="/run/user/$(id -u)/emacs/"
 
 get_listener () {
@@ -40,12 +43,34 @@ get_listener () {
     fi
 }
 
+maybe_notify () {
+    echo >&2 "$1"
+    [ -n "$XDG_RUNTIME_DIR" ] \
+	&& notify-send --urgency=low --expire-time=10000 "$1"
+}
+
+die_wedged () {
+    maybe_notify "in-tree Emacs appears to be wedged"
+    # Only exit non-zero if we were expected to start the daemon.
+    ! $may_start; exit
+}
+
+egrep_negate () {
+    echo -n "^([^${1:0:1}]"
+    for (( i=1; i < ${#1}; i++ )); do
+	echo -n "|(${1:0:$i}([^${1:$i:1}]|$))"
+    done
+    echo -n "|($1.+))"
+}
+
 for arg do
     shift
     case "$arg" in
 	'--spw/installed')               want_installed=true	 ;;
 	'--spw/no-start')                may_start=false	 ;;
 	'--spw/update-environment')      want_update=true	 ;;
+	'-V'|'--version')                want_version=true	 ;;&
+	'-e'|'--eval')                   want_eval=true          ;;&
 	'-s'|'--socket-name') min_arg=2; daemon_name="$1"        ;;&
 	'-s'?*)               min_arg=1; daemon_name="${arg:2}"  ;;&
 	'--socket-name='?*)   min_arg=1; daemon_name="${arg:14}" ;;&
@@ -81,10 +106,11 @@ if [ -z "$daemon_name" ] && $devel_running && $want_installed; then
 
     # Detach gdb so that Emacs can handle the SIGTERM.
     # We also have to quit gdb so that `gdb-inferior-status' is reset from
-    # "signal-received"; see `spw/gdbmacs-attach' command.
-    [ -n "$(get_listener ${socket_dir}gdbmacs)" ] \
-	&& emacsclient -sgdbmacs --eval '(gud-basic-call "detach")' \
-		       --eval '(gud-basic-call "quit")'
+    # "signal-received"; see `spw/gdbmacs-attach' function.
+    [ -n "${gdbmacs:=$(get_listener ${socket_dir}gdbmacs)}" ] \
+	&& "$installed_emacsclient" -sgdbmacs \
+				    --eval '(gud-basic-call "detach")' \
+				    --eval '(gud-basic-call "quit")'
 
     wait $inotifywait
     devel_running=false
@@ -106,6 +132,54 @@ if ! $want_installed && ! $installed_running \
 		       | xargs pwdx | grep -q "$HOME/src/emacs" ); then
     emacs="$devel_emacs"
     emacsclient="$devel_emacsclient"
+
+    # ---- Two special cases for primary session that's always under gdb
+    if [ -z "$daemon_name" ] && ! $want_version; then
+	# If devel Emacs is stopped or gdbmacs can't start it, ask gdbmacs to
+	# handle the request: it's probs. C-i e or editing a file via EDITOR.
+
+	[ -n "${gdbmacs:=$(get_listener ${socket_dir}gdbmacs)}" ] \
+	    && status=$("$installed_emacsclient" \
+			    -sgdbmacs \
+			    --eval \
+			    '(and (boundp '"'"'gud-comint-buffer)
+				  (get-buffer-process gud-comint-buffer)
+				  (string= "signal-received"
+					   gdb-inferior-status))')
+
+	if [ "$status" = t ]; then
+	    if $want_eval || $want_update; then
+		die_wedged
+	    else
+		pass_to_gdbmacs=true
+	    fi
+	elif [ -z "$listener" ]; then
+	    # inotifywait(1) in Debian "bullseye" doesn't have --include.
+	    inotifywait -qq -e create "${socket_dir}" \
+			--exclude "$(egrep_negate ${socket_dir}server)" &
+	    inotifywait=$!
+
+	    if "$installed_emacsclient" -a '' -sgdbmacs \
+					--eval '(spw/gdbmacs-attach)'; then
+		wait $inotifywait
+		listener=true
+	    elif $want_eval || $want_update; then
+		kill $inotifywait
+		die_wedged
+	    else
+		kill $inotifywait
+		pass_to_gdbmacs=true
+	    fi
+	fi
+
+	if $pass_to_gdbmacs; then
+	    emacs="$installed_emacs"
+	    emacsclient="$installed_emacsclient"
+	    listener="$gdbmacs"
+	    set -- "$@" -sgdbmacs
+	fi
+    fi
+    # ---- End two special cases for primary session that's always under gdb
 else
     emacs="$installed_emacs"
     emacsclient="$installed_emacsclient"