bug#56025: [PATCH v4] 29.0.50; em-extpipe-test-2 times out on EMBA and Cygwin

[Eli Zaretskii <eliz@gnu.org>]

> From: Jim Porter <jporterbugs@gmail.com>
> Cc: larsi@gnus.org, 56025@debbugs.gnu.org
> Date: Sat, 23 Jul 2022 22:29:28 -0700
> 
> -@defun process-tty-name process
> +@defun process-tty-name process &optional stream
>  This function returns the terminal name that @var{process} is using for
>  its communication with Emacs---or @code{nil} if it is using pipes
>  instead of a pty (see @code{process-connection-type} in
> -@ref{Asynchronous Processes}).  If @var{process} represents a program
> -running on a remote host, the terminal name used by that program on
> -the remote host is provided as process property @code{remote-tty}.  If
> -@var{process} represents a network, serial, or pipe connection, the
> -value is @code{nil}.
> +@ref{Asynchronous Processes}).  If @var{stream} is one of @code{stdin},
> +@code{stdout}, or @code{stderr}, this function returns the terminal
> +name (or @code{nil}, as above) that @var{process} uses for that stream
> +specifically.  You can use this to determine whether a particular
> +stream uses a pipe or a pty.

This text doesn't tell what happens if STREAM is nil or omitted.

> +If @var{process} represents a program running on a remote host, the
> +terminal name used by that program on the remote host is provided as
> +process property @code{remote-tty}.  If @var{process} represents a
> +network, serial, or pipe connection, the value is @code{nil}.

If the previous paragraph is only for local subprocesses, the text
there should say so.

>  @end defun
>  
>  @defun process-coding-system process
> diff --git a/etc/NEWS b/etc/NEWS
> index dc79f0826a..23777d349e 100644
> --- a/etc/NEWS
> +++ b/etc/NEWS
> @@ -3198,7 +3198,10 @@ invocation.  Such shells are POSIX conformant by default.
>  ** 'make-process' can set connection type independently for input and output.
>  When calling 'make-process', communication via pty can be enabled
>  selectively for just input or output by passing a cons cell for
> -':connection-type', e.g. '(pipe . pty)'.
> +':connection-type', e.g. '(pipe . pty)'.  When examining a process
> +later, you can determine whether a particular stream for a process
> +uses a pty by passing one of 'stdin', 'stdout', or 'stderr' as the
> +second argument to 'process-tty-name'.
>  
>  +++
>  ** 'signal-process' now consults the list 'signal-process-functions'.
> diff --git a/lisp/eshell/esh-io.el b/lisp/eshell/esh-io.el
> index c035890ddf..68e52a2c9c 100644
> --- a/lisp/eshell/esh-io.el
> +++ b/lisp/eshell/esh-io.el
> @@ -276,18 +276,21 @@ eshell-close-target
>     ;; If we're redirecting to a process (via a pipe, or process
>     ;; redirection), send it EOF so that it knows we're finished.
>     ((eshell-processp target)
> -    ;; According to POSIX.1-2017, section 11.1.9, sending EOF causes
> -    ;; all bytes waiting to be read to be sent to the process
> -    ;; immediately.  Thus, if there are any bytes waiting, we need to
> -    ;; send EOF twice: once to flush the buffer, and a second time to
> -    ;; cause the next read() to return a size of 0, indicating
> -    ;; end-of-file to the reading process.  However, some platforms
> -    ;; (e.g. Solaris) actually require sending a *third* EOF.  Since
> -    ;; sending extra EOFs while the process is running shouldn't break
> -    ;; anything, we'll just send the maximum we'd ever need.  See
> -    ;; bug#56025 for further details.
> -    (let ((i 0))
> -      (while (and (<= (cl-incf i) 3)
> +    ;; According to POSIX.1-2017, section 11.1.9, when communicating
> +    ;; via terminal, sending EOF causes all bytes waiting to be read
> +    ;; to be sent to the process immediately.  Thus, if there are any
> +    ;; bytes waiting, we need to send EOF twice: once to flush the
> +    ;; buffer, and a second time to cause the next read() to return a
> +    ;; size of 0, indicating end-of-file to the reading process.
> +    ;; However, some platforms (e.g. Solaris) actually require sending
> +    ;; a *third* EOF.  Since sending extra EOFs while the process is
> +    ;; running are a no-op, we'll just send the maximum we'd ever
> +    ;; need.  See bug#56025 for further details.
> +    (let ((i 0)
> +          ;; Only call `process-send-eof' once if communicating via a
> +          ;; pipe (in truth, this just closes the pipe).
> +          (max-attempts (if (process-tty-name target 'stdin) 3 1)))
> +      (while (and (<= (cl-incf i) max-attempts)
>                    (eq (process-status target) 'run))
>          (process-send-eof target))))
>  
> diff --git a/src/process.c b/src/process.c
> index da5e9cb182..adc508156f 100644
> --- a/src/process.c
> +++ b/src/process.c
> @@ -1243,14 +1243,29 @@ DEFUN ("process-command", Fprocess_command, Sprocess_command, 1, 1, 0,
>    return XPROCESS (process)->command;
>  }
>  
> -DEFUN ("process-tty-name", Fprocess_tty_name, Sprocess_tty_name, 1, 1, 0,
> +DEFUN ("process-tty-name", Fprocess_tty_name, Sprocess_tty_name, 1, 2, 0,
>         doc: /* Return the name of the terminal PROCESS uses, or nil if none.
>  This is the terminal that the process itself reads and writes on,
> -not the name of the pty that Emacs uses to talk with that terminal.  */)
> -  (register Lisp_Object process)
> +not the name of the pty that Emacs uses to talk with that terminal.
> +
> +If STREAM is one of `stdin', `stdout', or `stderr', return the name of
> +the terminal PROCESS uses for that stream.  This can be used to detect
> +whether a particular stream is connected via a pipe or a pty.  */)
> +  (register Lisp_Object process, Lisp_Object stream)

Same here: the call without the optional argument returns something
whose relation to the value when STREAM is non-nil is not clear from
the doc string.

Thanks.