5 files changed, 40 insertions, 51 deletions

diff --git a/lisp/progmodes/gdb-mi.el b/lisp/progmodes/gdb-mi.el
index f5e1abdd546..8e15ec6584e 100644
--- a/lisp/progmodes/gdb-mi.el
+++ b/lisp/progmodes/gdb-mi.el
@@ -574,21 +574,20 @@ NOARG must be t when this macro is used outside `gud-def'"
     (concat (gdb-gud-context-command ,cmd1 ,noall) " " ,cmd2)
     ,(when (not noarg) 'arg)))
 
-(defun gdb--check-interpreter (proc string)
+(defun gdb--check-interpreter (filter proc string)
   (unless (zerop (length string))
-    (let ((filter (process-get proc 'gud-normal-filter)))
-      (set-process-filter proc filter)
-      (unless (memq (aref string 0) '(?^ ?~ ?@ ?& ?* ?=))
-        ;; Apparently we're not running with -i=mi.
-        (let ((msg "Error: you did not specify -i=mi on GDB's command line!"))
-          (message msg)
-          (setq string (concat (propertize msg 'font-lock-face 'error)
-                               "\n" string)))
-        ;; Use the old gud-gbd filter, not because it works, but because it
-        ;; will properly display GDB's answers rather than hanging waiting for
-        ;; answers that aren't coming.
-        (set (make-local-variable 'gud-marker-filter) #'gud-gdb-marker-filter))
-      (funcall filter proc string))))
+    (remove-function (process-filter proc) #'gdb--check-interpreter)
+    (unless (memq (aref string 0) '(?^ ?~ ?@ ?& ?* ?=))
+      ;; Apparently we're not running with -i=mi.
+      (let ((msg "Error: you did not specify -i=mi on GDB's command line!"))
+        (message msg)
+        (setq string (concat (propertize msg 'font-lock-face 'error)
+                             "\n" string)))
+      ;; Use the old gud-gbd filter, not because it works, but because it
+      ;; will properly display GDB's answers rather than hanging waiting for
+      ;; answers that aren't coming.
+      (set (make-local-variable 'gud-marker-filter) #'gud-gdb-marker-filter))
+    (funcall filter proc string)))
 
 (defvar gdb-control-level 0)
 
@@ -662,8 +661,7 @@ detailed description of this mode.
   ;; Setup a temporary process filter to warn when GDB was not started
   ;; with -i=mi.
   (let ((proc (get-buffer-process gud-comint-buffer)))
-    (process-put proc 'gud-normal-filter (process-filter proc))
-    (set-process-filter proc #'gdb--check-interpreter))
+    (add-function :around (process-filter proc) #'gdb--check-interpreter))
 
   (set (make-local-variable 'gud-minor-mode) 'gdbmi)
   (set (make-local-variable 'gdb-control-level) 0)
diff --git a/lisp/progmodes/gud.el b/lisp/progmodes/gud.el
index 4e31c5e827c..6076f88dea6 100644
--- a/lisp/progmodes/gud.el
+++ b/lisp/progmodes/gud.el
@@ -3387,9 +3387,6 @@ ACTIVATEP non-nil means activate mouse motion events."
 
 ;;; Tips for `gud'
 
-(defvar gud-tooltip-original-filter nil
-  "Process filter to restore after GUD output has been received.")
-
 (defvar gud-tooltip-dereference nil
   "Non-nil means print expressions with a `*' in front of them.
 For C this would dereference a pointer expression.")
@@ -3423,7 +3420,7 @@ With arg, dereference expr if ARG is positive, otherwise do not dereference."
 ; gdb-mi.el gets round this problem.
 (defun gud-tooltip-process-output (process output)
   "Process debugger output and show it in a tooltip window."
-  (set-process-filter process gud-tooltip-original-filter)
+  (remove-function (process-filter process) #'gud-tooltip-process-output)
   (tooltip-show (tooltip-strip-prompt process output)
                 (or gud-tooltip-echo-area tooltip-use-echo-area)))
 
@@ -3490,8 +3487,8 @@ so they have been disabled."))
                       (gdb-input
                        (concat cmd "\n")
                        `(lambda () (gdb-tooltip-print ,expr))))
-                  (setq gud-tooltip-original-filter (process-filter process))
-                  (set-process-filter process 'gud-tooltip-process-output)
+                  (add-function :override (process-filter process)
+                                #'gud-tooltip-process-output)
                   (gud-basic-call cmd))
                 expr))))))))
 
diff --git a/lisp/progmodes/octave-inf.el b/lisp/progmodes/octave-inf.el
index de7ca32befe..4a227db7164 100644
--- a/lisp/progmodes/octave-inf.el
+++ b/lisp/progmodes/octave-inf.el
@@ -348,9 +348,9 @@ the rest to `inferior-octave-output-string'."
 The elements of LIST have to be strings and are sent one by one.  All
 output is passed to the filter `inferior-octave-output-digest'."
   (let* ((proc inferior-octave-process)
-         (filter (process-filter proc))
          string)
-    (set-process-filter proc 'inferior-octave-output-digest)
+    (add-function :override (process-filter proc)
+                  #'inferior-octave-output-digest)
     (setq inferior-octave-output-list nil)
     (unwind-protect
         (while (setq string (car list))
@@ -360,7 +360,8 @@ output is passed to the filter `inferior-octave-output-digest'."
           (while inferior-octave-receive-in-progress
             (accept-process-output proc))
           (setq list (cdr list)))
-      (set-process-filter proc filter))))
+      (remove-function (process-filter proc)
+                       #'inferior-octave-output-digest))))
 
 (defun inferior-octave-directory-tracker (string)
   "Tracks `cd' commands issued to the inferior Octave process.
diff --git a/lisp/progmodes/prolog.el b/lisp/progmodes/prolog.el
index 85e4172c8fe..8971e97a44e 100644
--- a/lisp/progmodes/prolog.el
+++ b/lisp/progmodes/prolog.el
@@ -1770,7 +1770,8 @@ This function must be called from the source code buffer."
                                              real-file))
     (with-current-buffer buffer
       (goto-char (point-max))
-      (set-process-filter process 'prolog-consult-compile-filter)
+      (add-function :override (process-filter process)
+                    #'prolog-consult-compile-filter)
       (process-send-string "prolog" command-string)
       ;; (prolog-build-prolog-command compilep file real-file first-line))
       (while (and prolog-process-flag
@@ -1781,7 +1782,8 @@ This function must be called from the source code buffer."
       (insert (if compilep
                   "\nCompilation finished.\n"
                 "\nConsulted.\n"))
-      (set-process-filter process old-filter))))
+      (remove-function (process-filter process)
+                       #'prolog-consult-compile-filter))))
 
 (defvar compilation-error-list)
 
diff --git a/lisp/progmodes/xscheme.el b/lisp/progmodes/xscheme.el
index 2ad44b4b1c8..37c3cd37a6c 100644
--- a/lisp/progmodes/xscheme.el
+++ b/lisp/progmodes/xscheme.el
@@ -35,7 +35,6 @@
 ;;;; Internal Variables
 
 (defvar xscheme-previous-mode)
-(defvar xscheme-previous-process-state)
 (defvar xscheme-last-input-end)
 
 (defvar xscheme-process-command-line nil
@@ -388,8 +387,6 @@ with no args, if that value is non-nil.
   (if (not preserve)
       (let ((previous-mode major-mode))
         (kill-all-local-variables)
-        (make-local-variable 'xscheme-process-name)
-        (make-local-variable 'xscheme-previous-process-state)
         (make-local-variable 'xscheme-runlight-string)
         (make-local-variable 'xscheme-runlight)
         (set (make-local-variable 'xscheme-previous-mode) previous-mode)
@@ -397,35 +394,29 @@ with no args, if that value is non-nil.
           (set (make-local-variable 'xscheme-buffer-name) (buffer-name buffer))
           (set (make-local-variable 'xscheme-last-input-end) (make-marker))
           (let ((process (get-buffer-process buffer)))
-            (if process
-                (progn
-                  (setq xscheme-process-name (process-name process))
-                  (setq xscheme-previous-process-state
-                        (cons (process-filter process)
-                              (process-sentinel process)))
-                  (xscheme-process-filter-initialize t)
-                  (xscheme-mode-line-initialize xscheme-buffer-name)
-                  (set-process-sentinel process 'xscheme-process-sentinel)
-                  (set-process-filter process 'xscheme-process-filter))
-                (setq xscheme-previous-process-state (cons nil nil)))))))
+            (when process
+              (setq-local xscheme-process-name (process-name process))
+              ;; FIXME: Use add-function!
+              (xscheme-process-filter-initialize t)
+              (xscheme-mode-line-initialize xscheme-buffer-name)
+              (add-function :override (process-sentinel process)
+                            #'xscheme-process-sentinel)
+              (add-function :override (process-filter process)
+                            #'xscheme-process-filter))))))
   (scheme-interaction-mode-initialize)
   (scheme-mode-variables)
   (run-mode-hooks 'scheme-mode-hook 'scheme-interaction-mode-hook))
 
 (defun exit-scheme-interaction-mode ()
-  "Take buffer out of scheme interaction mode"
+  "Take buffer out of scheme interaction mode."
   (interactive)
   (if (not (derived-mode-p 'scheme-interaction-mode))
       (error "Buffer not in scheme interaction mode"))
-  (let ((previous-state xscheme-previous-process-state))
-    (funcall xscheme-previous-mode)
-    (let ((process (get-buffer-process (current-buffer))))
-      (if process
-          (progn
-            (if (eq (process-filter process) 'xscheme-process-filter)
-                (set-process-filter process (car previous-state)))
-            (if (eq (process-sentinel process) 'xscheme-process-sentinel)
-                (set-process-sentinel process (cdr previous-state))))))))
+  (funcall xscheme-previous-mode)
+  (let ((process (get-buffer-process (current-buffer))))
+    (when process
+      (remove-function (process-sentinel process) #'xscheme-process-sentinel)
+      (remove-function (process-filter process) #'xscheme-process-filter))))
 
 (defvar scheme-interaction-mode-commands-alist nil)
 (defvar scheme-interaction-mode-map nil)