* doc/lispref/os.texi (Killing Emacs):
* src/emacs.c (Fkill_emacs): Document what non-integer, non-string
argument to 'kill-emacs' means. (Bug#42400)
If @var{exit-data} is a string, its contents are stuffed into the
terminal input buffer so that the shell (or whatever program next reads
input) can read them.
+
+If @var{exit-data} is neither an integer nor a string, or is omitted,
+that means to use the (system-specific) exit status which indicates
+successful program termination.
@end deffn
@cindex SIGTERM
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.
+Any other value of ARG, or ARG omitted, means return an
+exit code that indicates successful program termination.
This function is called upon receipt of the signals SIGTERM
or SIGHUP, and upon SIGINT in batch mode.