bug#30244: 25.2.50; Killing sql mode buffer results in error

bug#30244: 25.2.50; Killing sql mode buffer results in error

[Allen Li]

To reproduce (need a mysql server handy):

M-x toggle-debug-on-error RET
M-x sql-mysql RET <fill in information>
C-x k RET yes RET

Yields error:

Debugger entered--Lisp error: (error "Selecting deleted buffer")
  sql-stop(#<process SQL> "hangup\n")

In GNU Emacs 25.2.50.1 (x86_64-pc-linux-gnu, GTK+ Version 3.22.11),
modified by Debian

bug#30244: 25.2.50; Killing sql mode buffer results in error

[Lars Ingebrigtsen]

Allen Li <vianchielfaura@gmail.com> writes:

> To reproduce (need a mysql server handy):
>
> M-x toggle-debug-on-error RET
> M-x sql-mysql RET <fill in information>
> C-x k RET yes RET
>
> Yields error:
>
> Debugger entered--Lisp error: (error "Selecting deleted buffer")
>   sql-stop(#<process SQL> "hangup\n")

I don't use sql-mode, so I can't test this.  Does the following trivial
patch work fix the bug for you?

diff --git a/lisp/progmodes/sql.el b/lisp/progmodes/sql.el
index f907a01d8c..ebbef8d89e 100644
--- a/lisp/progmodes/sql.el
+++ b/lisp/progmodes/sql.el
@@ -4031,15 +4031,16 @@ sql-stop
 
 This function is a sentinel watching the SQL interpreter process.
 Sentinels will always get the two parameters PROCESS and EVENT."
-  (with-current-buffer (process-buffer process)
-    (let
-        ((comint-input-ring-separator sql-input-ring-separator)
-         (comint-input-ring-file-name sql-input-ring-file-name))
-      (comint-write-input-ring))
-
-    (if (not buffer-read-only)
-        (insert (format "\nProcess %s %s\n" process event))
-      (message "Process %s %s" process event))))
+  (when (buffer-live-p (process-buffer process))
+    (with-current-buffer (process-buffer process)
+      (let
+          ((comint-input-ring-separator sql-input-ring-separator)
+           (comint-input-ring-file-name sql-input-ring-file-name))
+        (comint-write-input-ring))
+
+      (if (not buffer-read-only)
+          (insert (format "\nProcess %s %s\n" process event))
+        (message "Process %s %s" process event)))))
 
 \f
 


-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#30244: 25.2.50; Killing sql mode buffer results in error

[Phil Sainty]

I can replicate this with `sql-postgres', and can confirm that
the `buffer-live-p' wrapper eliminates the error here

bug#30244: 25.2.50; Killing sql mode buffer results in error

[Lars Ingebrigtsen]

Phil Sainty <psainty@orcon.net.nz> writes:

> I can replicate this with `sql-postgres', and can confirm that
> the `buffer-live-p' wrapper eliminates the error here

Thanks for testing.

I've now applied the patch to Emacs 27.1.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no