emacs-29 8f23a02a9ea: Fix updating process-mark position in 'set-process-buffer'

[Eli Zaretskii]

branch: emacs-29
commit 8f23a02a9ea1fbc4213cae5664dcb9bf6b5205f6
Author: Eli Zaretskii <eliz@gnu.org>
Commit: Eli Zaretskii <eliz@gnu.org>

    Fix updating process-mark position in 'set-process-buffer'
    
    * src/process.c (update_process_mark): Update marker position only
    if P's process-mark is not already associated with P's buffer.
    (Bug#66313)
---
 src/process.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/process.c b/src/process.c
index 5f7408a9395..46e57c1a7c2 100644
--- a/src/process.c
+++ b/src/process.c
@@ -1273,7 +1273,8 @@ static void
 update_process_mark (struct Lisp_Process *p)
 {
   Lisp_Object buffer = p->buffer;
-  if (BUFFERP (buffer))
+  if (BUFFERP (buffer)
+      && XMARKER (p->mark)->buffer != XBUFFER (buffer))
     set_marker_both (p->mark, buffer,
                     BUF_ZV (XBUFFER (buffer)),
                     BUF_ZV_BYTE (XBUFFER (buffer)));