bug#5819: 23.1.93; OSX: start-process sometimes returns an unready process

[Markus Triska]

Let testprocess.el consist of the following form:

    (let (p (n 1))
      (while t
        (message "iteration %s" n)
        (setq n (1+ n)
              p (start-process "bc" nil "bc"))
        (process-send-string p "test")
        (delete-process p)))

On OSX 10.4, when I do "$ emacs -Q --script testprocess.el", I get:

   $ emacs -Q --script testprocess.el
   iteration 1
   iteration 2
   iteration 3
   writing to process: Input/output error, bc

and sometimes, particularly under high system load:

   $ emacs -Q --script testprocess.el
   iteration 1
   iteration 2
   Process bc not running

The number of iterations often varies over invocations.

In GNU Emacs 23.1.93.1 (i386-apple-darwin8.11.1)
 of 2010-04-01 on mt-computer.local
configured using `configure  '--without-x''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: nil
  value of $XMODIFIERS: nil
  locale-coding-system: nil
  default enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t