bug#71223: 30.0.50; stack overflow after very fast opening and closing of frames

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

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Hi Daniel,

Could you try the patch below which sequentializes the processing of the
process-filters to avoid such recursion?


        Stefan

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diff --git a/lisp/server.el b/lisp/server.el
index b65053267a6..7d8b8d37fad 100644
--- a/lisp/server.el
+++ b/lisp/server.el
@@ -1046,6 +1046,8 @@ server-execute-continuation
     (process-put proc 'continuation nil)
     (if continuation (ignore-errors (funcall continuation)))))
 
+(defvar server--pending-filter-calls t)
+
 (cl-defun server-process-filter (proc string)
   "Process a request from the server to edit some files.
 PROC is the server process.  STRING consists of a sequence of
@@ -1145,6 +1147,18 @@ server-process-filter
 `-suspend'
   Suspend this terminal, i.e., stop the client process.
   Sent when the user presses \\[suspend-frame]."
+  (if (listp server--pending-filter-calls)
+      ;; We're already running another instance of this process filter.
+      ;; Let's make sure we don't run them in a nested fashion.
+      (push (cons proc string) server--pending-filter-calls)
+    (let ((server--pending-filter-calls nil))
+     (push (cons proc string) server--pending-filter-calls)
+     (while server--pending-filter-calls
+       (dolist (pending-call (prog1 (nreverse server--pending-filter-calls)
+                               (setq server--pending-filter-calls nil)))
+         (server--process-filter (car pending-call) (cdr pending-call)))))))
+
+(cl-defun server--process-filter (proc string)
   (server-log (concat "Received " string) proc)
   ;; First things first: let's check the authentication
   (unless (process-get proc :authenticated)
@@ -1159,6 +1173,9 @@ server-process-filter
       ;; it, in case the error written by emacsclient to stderr is not
       ;; visible for some reason.
       (message "Authentication failed")
+      ;; FIXME: Ideally we should not need `sit-for' here and instead use
+      ;; some `message-timed' call which makes sure the message is visible
+      ;; without forcing us to wait here.
       (sit-for 2)
       (server-send-string
        proc (concat "-error " (server-quote-arg "Authentication failed")))
@@ -1169,10 +1186,9 @@ server-process-filter
 	    (delete-terminal terminal))))
       ;; Before calling `delete-process', give emacsclient time to
       ;; receive the error string and shut down on its own.
-      (sit-for 1)
-      (delete-process proc)
+      (run-with-timer 1 nil #'delete-process proc)
       ;; We return immediately.
-      (cl-return-from server-process-filter)))
+      (cl-return-from server--process-filter)))
   (let ((prev (process-get proc 'previous-string)))
     (when prev
       (setq string (concat prev string))
@@ -1508,6 +1524,9 @@ server-return-error
     ;; it, in case the error written by emacsclient to stderr is not
     ;; visible for some reason.
     (message (error-message-string err))
+    ;; FIXME: Ideally we should not need `sit-for' here and instead use
+    ;; some `message-timed' call which makes sure the message is visible
+    ;; without forcing us to wait here.
     (sit-for 2)
     (server-send-string
      proc (concat "-error " (server-quote-arg
@@ -1520,7 +1539,7 @@ server-return-error
 	  (delete-terminal terminal))))
     ;; Before calling `delete-process', give emacsclient time to
     ;; receive the error string and shut down on its own.
-    (sit-for 5)
+    (run-with-timer 5 nil #'delete-process proc)
     (delete-process proc)))
 
 (defun server-goto-line-column (line-col)