Debugging Emacs Issues

• Be vigilant. Is there any issue in Emacs that annoys you, even barely noticably? Do not tolerate such issues! If you are a tolerant person, this may be tough for you at first. However, there is no need to accept wrong programs! By improving a program, you will improve your own environment and also that of many others.
• Try searching with brute force. Many issues can be triggered by simply repeatedly performing one or two simple steps in an automated way. This is well worth trying and can expose memory leaks, rare timing issues and several other problems.
• Use Emacs's built-in features to verify internal properties. For example, see Ami Fischman's ingenious approach for tracking down a memory leak. You can set a timer to continuously perform such tasks in the background.
• Be diligent. Very often, you will need to slow down, because you will run into too many issues at once to keep track of all of them if you are going too fast.

• Hang: Sometimes, particularly after a network connection, Emacs would simply hang, and could no longer be interrupted with C-g.
• Crash: Sometimes, Emacs would simply crash, especially when using M-<.
• No flyspell: Sometimes, flyspell was unexpectedly simply disabled, even though I had enabled it and relied on it for spellchecking.

(let ((n 0))
  (with-temp-buffer
    (insert "test")
    (while t
      (setq n (1+ n))
      (when (= (mod n 100) 0)
        (message "n: %s -- %s" n (emacs-uptime)))
      (ispell-word nil t))))
    

while true; do echo "-"; done | aspell -a
    

1. invoke ps from within Emacs
2. write its output into a temporary buffer
3. use automated text search to see whether "aspell" appears in that buffer. If it doesn't, then aspell has stopped running.

(defun aspell-alive-p ()
  (with-temp-buffer
    (let ((p (start-process "ps" (current-buffer) "ps" "-A")))
      (while (eq (process-status p) 'run)
        (accept-process-output p nil nil t))
      (goto-char (point-min))
      (search-forward-regexp
       (format "%s.*aspell" (process-id ispell-process)) nil t))))
    

(with-temp-buffer (start-process "ps" (current-buffer) "ps"))
    

(defun my-flyspell-check ()
  (unless (memq 'flyspell-post-command-hook post-command-hook)
    (when flyspell-mode
      (with-current-buffer (get-buffer-create "flywarn")
        (insert "Flyspell no longer active!\n"))
      (display-buffer  "flywarn"))))

(setq flycheck-timer (run-with-timer 0 0.5 'my-flyspell-check))
    

;; 1) emacs -Q f.el -f eval-buffer
;; 2) M-x gnus RET q y
;;    M-x gnus RET q y
;; 3) M-! killall -9 aspell RET
;; 4) M-x gnus RET q y


(defun reactivate-flyspell ()
  (unless (memq 'flyspell-post-command-hook post-command-hook)
    (flyspell-mode 1)))

(setq my-idle (run-with-idle-timer 0.1 t 'reactivate-flyspell))
    

diff --git a/src/process.c b/src/process.c
index b0bebeb..b5aebdc 100644
--- a/src/process.c
+++ b/src/process.c
@@ -3366,7 +3374,7 @@ usage: (make-network-process &rest ARGS)  */)
       hints.ai_protocol = 0;
 
 #ifdef HAVE_RES_INIT
-      res_init ();
+      /* res_init (); */
 #endif
 
       ret = getaddrinfo (SDATA (host), portstring, &hints, &res);
    

(progn
  (find-file "~/emacs/etc/images/splash.svg")
  (while t
    (image-toggle-display)
    (redisplay)))
    

(let ((n 0))
  (while t
    (setq n (1+ n))
    (message "iteration: %s" n)
    (delete-process (start-process "bc" nil "bc"))))