Improve error messaging when parent archive buffers are missing

* lisp/arc-mode.el (archive-write-file-member):
* lisp/tar-mode.el (tar-subfile-save-buffer): Give a better error
message when the parent buffer is dead (bug#56605).

2 files changed, 4 insertions, 0 deletions

diff --git a/lisp/arc-mode.el b/lisp/arc-mode.el
index c52f2a44322..35189f1bfd8 100644
--- a/lisp/arc-mode.el
+++ b/lisp/arc-mode.el
@@ -1318,6 +1318,8 @@ NEW-NAME."
 ;;; Section: IO stuff
 
 (defun archive-write-file-member ()
+  (unless (buffer-live-p archive-superior-buffer)
+    (error "The archive buffer no longer exists; can't save"))
   (save-excursion
     (save-restriction
       (message "Updating archive...")
diff --git a/lisp/tar-mode.el b/lisp/tar-mode.el
index 7b5a869ab57..d7a09789699 100644
--- a/lisp/tar-mode.el
+++ b/lisp/tar-mode.el
@@ -1329,6 +1329,8 @@ to make your changes permanent."
       (error "This buffer has no superior tar file buffer"))
   (if (not (and (boundp 'tar-superior-descriptor) tar-superior-descriptor))
       (error "This buffer doesn't have an index into its superior tar file!"))
+  (unless (buffer-live-p tar-superior-buffer)
+    (error "The tar buffer no longer exists; can't save"))
   (let ((subfile (current-buffer))
         (coding buffer-file-coding-system)
         (descriptor tar-superior-descriptor)