upstream

1 files changed, 20 insertions, 7 deletions

diff --git a/src/undo.c b/src/undo.c
index 1cb048690ba..c90e7b62405 100644
--- a/src/undo.c
+++ b/src/undo.c
@@ -226,7 +226,7 @@ record_first_change (void)
     base_buffer = base_buffer->base_buffer;
 
   BVAR (current_buffer, undo_list) =
-    Fcons (Fcons (Qt, INTEGER_TO_CONS (base_buffer->modtime)),
+    Fcons (Fcons (Qt, make_lisp_time (base_buffer->modtime)),
            BVAR (current_buffer, undo_list));
 }
 
@@ -438,8 +438,8 @@ truncate_undo_list (struct buffer *b)
   unbind_to (count, Qnil);
 }
 
-static void user_error (const char*) NO_RETURN;
-static void user_error (const char *msg)
+static _Noreturn void
+user_error (const char *msg)
 {
   xsignal1 (Quser_error, build_string (msg));
 }
@@ -505,10 +505,23 @@ Return what remains of the list.  */)
               cdr = XCDR (next);
               if (EQ (car, Qt))
                 {
-                  /* Element (t high . low) records previous modtime.  */
+                  /* Element (t . TIME) records previous modtime.
+                     Preserve any flag of NONEXISTENT_MODTIME_NSECS or
+                     UNKNOWN_MODTIME_NSECS.  */
                   struct buffer *base_buffer = current_buffer;
-                  time_t mod_time;
-                  CONS_TO_INTEGER (cdr, time_t, mod_time);
+                  EMACS_TIME mod_time;
+
+                  if (CONSP (cdr)
+                      && CONSP (XCDR (cdr))
+                      && CONSP (XCDR (XCDR (cdr)))
+                      && CONSP (XCDR (XCDR (XCDR (cdr))))
+                      && INTEGERP (XCAR (XCDR (XCDR (XCDR (cdr)))))
+                      && XINT (XCAR (XCDR (XCDR (XCDR (cdr))))) < 0)
+                    mod_time =
+                      (make_emacs_time
+                       (0, XINT (XCAR (XCDR (XCDR (XCDR (cdr))))) / 1000));
+                  else
+                    mod_time = lisp_time_argument (cdr);
 
                   if (current_buffer->base_buffer)
                     base_buffer = current_buffer->base_buffer;
@@ -516,7 +529,7 @@ Return what remains of the list.  */)
                   /* If this records an obsolete save
                      (not matching the actual disk file)
                      then don't mark unmodified.  */
-                  if (mod_time != base_buffer->modtime)
+                  if (EMACS_TIME_NE (mod_time, base_buffer->modtime))
                     continue;
 #ifdef CLASH_DETECTION
                   Funlock_buffer ();