GNU bug report logs - #76786
31.0.50; condition-case's `debug` causes Emacs to exit when in batch mode

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Subject: bug#76786: closed (Re: bug#76786: 31.0.50; condition-case's
 `debug` causes Emacs to exit when in batch mode)
Date: Thu, 06 Mar 2025 18:08:02 +0000

[Message part 1 (text/plain, inline)]

Your bug report

#76786: 31.0.50; condition-case's `debug` causes Emacs to exit when in batch mode

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 76786 <at> debbugs.gnu.org.

-- 
76786: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=76786
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: 76786-done <at> debbugs.gnu.org
Subject: Re: bug#76786: 31.0.50; condition-case's `debug` causes Emacs to
 exit when in batch mode
Date: Thu, 06 Mar 2025 13:06:54 -0500

I pushed the fix below to `master`.
It took me a while to find the place where we short-circuited the normal
processing, to be honest (it was in `debug`).
And digging into its history doesn't completely explain why it's ever
been there, but I think it explains why it wasn't harmful back then
(`signal_or_quit` would have done the same anyway).


        Stefan


diff --git a/lisp/emacs-lisp/debug.el b/lisp/emacs-lisp/debug.el
index 0ca3a0f931c..f8af6eafa32 100644
--- a/lisp/emacs-lisp/debug.el
+++ b/lisp/emacs-lisp/debug.el
@@ -253,11 +253,11 @@ debug
 		    ;; Place an extra debug-on-exit for macro's.
 		    (when (eq 'lambda (car-safe (cadr (backtrace-frame 1 base))))
 		      (backtrace-debug 2 t base))))
-                (with-current-buffer debugger-buffer
-                  (unless (derived-mode-p 'debugger-mode)
-	            (debugger-mode))
-	          (debugger-setup-buffer debugger-args)
-	          (when non-interactive-frame
+                (set-buffer debugger-buffer)
+                (unless (derived-mode-p 'debugger-mode)
+	          (debugger-mode))
+	        (debugger-setup-buffer debugger-args)
+	        (if non-interactive-frame
 		    ;; If the backtrace is long, save the beginning
 		    ;; and the end, but discard the middle.
                     (let ((inhibit-read-only t))
@@ -269,9 +269,8 @@
 		          (goto-char (point-max))
 		          (forward-line (- (/ debugger-batch-max-lines 2)))
 		          (delete-region middlestart (point)))
-		        (insert "...\n")))
-		    (message "%s" (buffer-string))
-		    (kill-emacs -1)))
+		        (insert "...\n"))
+		      (message "%s" (buffer-string)))
 	        (pop-to-buffer
 	         debugger-buffer
 	         `((display-buffer-reuse-window
@@ -300,7 +299,7 @@
 		  (message "")
 		  ;; Make sure we unbind buffer-read-only in the right buffer.
 		  (save-excursion
-		    (recursive-edit))))
+		      (recursive-edit)))))
 	    (when (and (window-live-p debugger-window)
 		       (eq (window-buffer debugger-window) debugger-buffer))
 	      ;; Record height of debugger window.

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From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: bug-gnu-emacs <at> gnu.org
Subject: 31.0.50; condition-case's `debug` causes Emacs to exit when in
 batch mode
Date: Thu, 06 Mar 2025 12:20:28 -0500

Package: Emacs
Version: 31.0.50


    % /usr/bin/emacs -Q --batch --eval '(setq debug-on-error t)' --eval '(progn (with-demoted-errors "A %S" (error "foo")) (message "B bar"))'
    Debugger entered--Lisp error: (error "foo")
      error("foo")
      (condition-case err (error "foo") ((debug error) (message "A %S" err) nil))
      (condition-case-unless-debug err (error "foo") (error (message "A %S" err) nil))
      (with-demoted-errors "A %S" (error "foo"))
      (progn (with-demoted-errors "A %S" (error "foo")) (message "B bar"))
      eval((progn (with-demoted-errors "A %S" (error "foo")) (message "B bar")) t)
      command-line-1(("--eval" "(setq debug-on-error t)" "--eval" "(progn (with-demoted-errors \"A %S\" (error \"foo\")) (message \"B bar\"))"))
      command-line()
      normal-top-level()
    
    % 

I'm happy to see a backtrace, but I should *also* see the

    A foo
    B bar

messages that I get to see when running this code without `--batch`.


        Stefan

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