4 files changed, 31 insertions, 40 deletions

diff --git a/src/emacs.c b/src/emacs.c
index 777ade9d825..6929886424f 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -2947,9 +2947,9 @@ sort_args (int argc, char **argv)
 DEFUN ("kill-emacs", Fkill_emacs, Skill_emacs, 0, 2, "P",
        doc: /* Exit the Emacs job and kill it.
 If ARG is an integer, return ARG as the exit program code.
-If ARG is a string, stuff it as keyboard input.  (This might
-not work on modern systems due to security considerations, or
-not at all.)
+If ARG is a string, stuff it and then a newline as keyboard input,
+if Emacs is running interactively on a terminal and the platform
+supports and allows stuffing; this may need special privileges.
 Any other value of ARG, or ARG omitted, means return an
 exit code that indicates successful program termination.
 
diff --git a/src/keyboard.c b/src/keyboard.c
index 648dd81660a..55fb2401f2b 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -12421,19 +12421,15 @@ DEFUN ("suspend-emacs", Fsuspend_emacs, Ssuspend_emacs, 0, 1, "",
 If `cannot-suspend' is non-nil, or if the system doesn't support job
 control, run a subshell instead.
 
-If optional arg STUFFSTRING is non-nil, its characters are stuffed
-to be read as terminal input by Emacs's parent, after suspension.
+If optional arg STUFFSTRING is non-nil, stuff it and then a newline as
+keyboard input, if Emacs is running interactively on a terminal and the
+platform supports and allows stuffing; this may need special privileges.
 
 Before suspending, run the normal hook `suspend-hook'.
 After resumption run the normal hook `suspend-resume-hook'.
 
 Some operating systems cannot stop the Emacs process and resume it later.
-On such systems, Emacs starts a subshell instead of suspending.
-
-On some operating systems, stuffing characters into terminal input
-buffer requires special privileges or is not supported at all.
-On such systems, calling this function with non-nil STUFFSTRING might
-either signal an error or silently fail to stuff the characters.  */)
+On such systems, Emacs starts a subshell instead of suspending.  */)
   (Lisp_Object stuffstring)
 {
   specpdl_ref count = SPECPDL_INDEX ();
@@ -12472,38 +12468,34 @@ either signal an error or silently fail to stuff the characters.  */)
   return Qnil;
 }
 
-/* If STUFFSTRING is a string, stuff its contents as pending terminal input.
-   Then in any case stuff anything Emacs has read ahead and not used.  */
+/* If STUFFSTRING is a string, stuff its contents and then a newline as
+   pending terminal input.  Then stuff anything Emacs has read ahead and
+   not used.  However, do nothing if stuffing does not work.  */
 
 void
 stuff_buffered_input (Lisp_Object stuffstring)
 {
 #ifdef SIGTSTP  /* stuff_char is defined if SIGTSTP.  */
-  register unsigned char *p;
+  int bad_stuff = 0;
 
   if (STRINGP (stuffstring))
     {
-      register ptrdiff_t count;
-
-      p = SDATA (stuffstring);
-      count = SBYTES (stuffstring);
-      while (count-- > 0)
-        stuff_char (*p++);
-      stuff_char ('\n');
+      char *p = SSDATA (stuffstring);
+      for (ptrdiff_t i = SBYTES (stuffstring); !bad_stuff && 0 < i; i--)
+        bad_stuff = stuff_char (*p++);
+      if (!bad_stuff)
+        bad_stuff = stuff_char ('\n');
     }
 
-  /* Anything we have read ahead, put back for the shell to read.  */
-  /* ?? What should this do when we have multiple keyboards??
-     Should we ignore anything that was typed in at the "wrong" kboard?
-
-     rms: we should stuff everything back into the kboard
-     it came from.  */
+  /* Anything we have read ahead, put back for the shell to read.
+     When we have multiple keyboards, we should stuff everything back
+     into the keyboard it came from, but fixing this is low priority as
+     many systems prohibit stuffing for security reasons.  */
   for (; kbd_fetch_ptr != kbd_store_ptr;
        kbd_fetch_ptr = next_kbd_event (kbd_fetch_ptr))
     {
-
-      if (kbd_fetch_ptr->kind == ASCII_KEYSTROKE_EVENT)
-        stuff_char (kbd_fetch_ptr->ie.code);
+      if (kbd_fetch_ptr->kind == ASCII_KEYSTROKE_EVENT && !bad_stuff)
+        bad_stuff = stuff_char (kbd_fetch_ptr->ie.code);
 
       clear_event (&kbd_fetch_ptr->ie);
     }
diff --git a/src/lisp.h b/src/lisp.h
index cefca3d6fbb..37c34dfbe84 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -5280,7 +5280,7 @@ maybe_disable_address_randomization (int argc, char **argv)
 extern int emacs_exec_file (char const *, char *const *, char *const *);
 extern void init_standard_fds (void);
 extern char *emacs_get_current_dir_name (void);
-extern void stuff_char (char c);
+extern int stuff_char (char c);
 extern void init_foreground_group (void);
 extern void sys_subshell (void);
 extern void sys_suspend (void);
diff --git a/src/sysdep.c b/src/sysdep.c
index 2f5572009fb..8895655566e 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -390,23 +390,22 @@ discard_tty_input (void)
 
 /* Arrange for character C to be read as the next input from
    the terminal.
+   Return 0 on success, -1 otherwise.
    XXX What if we have multiple ttys?
 */
 
-void
+int
 stuff_char (char c)
 {
-  if (! (FRAMEP (selected_frame)
-         && FRAME_LIVE_P (XFRAME (selected_frame))
-         && FRAME_TERMCAP_P (XFRAME (selected_frame))))
-    return;
-
 /* Should perhaps error if in batch mode */
 #ifdef TIOCSTI
-  ioctl (fileno (CURTTY()->input), TIOCSTI, &c);
-#else /* no TIOCSTI */
-  error ("Cannot stuff terminal input characters in this version of Unix");
+  if (FRAMEP (selected_frame)
+      && FRAME_LIVE_P (XFRAME (selected_frame))
+      && FRAME_TERMCAP_P (XFRAME (selected_frame)))
+    return ioctl (fileno (CURTTY()->input), TIOCSTI, &c);
 #endif /* no TIOCSTI */
+
+  return -1;
 }
 
 #endif /* SIGTSTP */