Fix #11961. Document STARTUPINFO and creation flag options.

diff --cc Doc/library/subprocess.rst
index 5677738456874207eaf1f158bae8f6be68eb13b0,932ca8b0841080a1a9baf7ed472575a57fa5ea8b..e09994ce7d56cec530391f6bbfbf4c9998930a39
--- 1/Doc/library/subprocess.rst
--- 2/Doc/library/subprocess.rst
+++ b/Doc/library/subprocess.rst
@@@ -212,19 -171,9 +212,20 @@@ This module defines one class called :c
        :attr:`stdout`, :attr:`stdin` and :attr:`stderr` are not updated by the
        :meth:`communicate` method.
  
-    The *startupinfo* and *creationflags*, if given, will be passed to the
-    underlying CreateProcess() function.  They can specify things such as appearance
-    of the main window and priority for the new process.  (Windows only)
+    If given, *startupinfo* will be a :class:`STARTUPINFO` object, which is
+    passed to the underlying ``CreateProcess`` function.
 -   *creationflags*, if given, can be :data:`CREATE_NEW_CONSOLE`. (Windows only)
++   *creationflags*, if given, can be :data:`CREATE_NEW_CONSOLE` or
++   :data:`CREATE_NEW_PROCESS_GROUP`. (Windows only)
 +
 +   Popen objects are supported as context managers via the :keyword:`with` statement,
 +   closing any open file descriptors on exit.
 +   ::
 +
 +      with Popen(["ifconfig"], stdout=PIPE) as proc:
 +          log.write(proc.stdout.read())
 +
 +   .. versionchanged:: 3.2
 +      Added context manager support.
  
  
  .. data:: PIPE
@@@ -482,6 -428,101 +483,109 @@@ The following attributes are also avail
     ``N`` (Unix only).
  
  
+ Windows Popen Helpers
+ ---------------------
+ 
+ The :class:`STARTUPINFO` class and following constants are only available
+ on Windows.
+ 
+ .. class:: STARTUPINFO()
+ 
+    Partial support of the Windows
+    `STARTUPINFO <http://msdn.microsoft.com/en-us/library/ms686331(v=vs.85).aspx>`__
+    structure is used for :class:`Popen` creation.
+ 
+    .. attribute:: dwFlags
+ 
+       A bit field that determines whether certain :class:`STARTUPINFO` members
+       are used when the process creates a window. ::
+ 
+          si = subprocess.STARTUPINFO()
+          si.dwFlags = subprocess.STARTF_USESTDHANDLES | subprocess.STARTF_USESHOWWINDOW
+ 
+    .. attribute:: hStdInput
+ 
+       If :attr:`dwFlags` specifies :data:`STARTF_USESTDHANDLES`, this member is
+       the standard input handle for the process. If :data:`STARTF_USESTDHANDLES`
+       is not specified, the default for standard input is the keyboard buffer.
+ 
+    .. attribute:: hStdOutput
+ 
+       If :attr:`dwFlags` specifies :data:`STARTF_USESTDHANDLES`, this member is
+       the standard output handle for the process. Otherwise, this member is
+       ignored and the default for standard output is the console window's
+       buffer.
+ 
+    .. attribute:: hStdError
+ 
+       If :attr:`dwFlags` specifies :data:`STARTF_USESTDHANDLES`, this member is
+       the standard error handle for the process. Otherwise, this member is
+       ignored and the default for standard error is the console window's buffer.
+ 
+    .. attribute:: wShowWindow
+ 
+       If :attr:`dwFlags` specifies :data:`STARTF_USESHOWWINDOW`, this member
+       can be any of the values that can be specified in the ``nCmdShow``
+       parameter for the
+       `ShowWindow <http://msdn.microsoft.com/en-us/library/ms633548(v=vs.85).aspx>`__
+       function, except for ``SW_SHOWDEFAULT``. Otherwise, this member is
+       ignored.
+ 
+       :data:`SW_HIDE` is provided for this attribute. It is used when
+       :class:`Popen` is called with ``shell=True``.
+ 
+ 
+ Constants
+ ^^^^^^^^^
+ 
+ The :mod:`subprocess` module exposes the following constants.
+ 
+ .. data:: STD_INPUT_HANDLE
+ 
+    The standard input device. Initially, this is the console input buffer,
+    ``CONIN$``.
+ 
+ .. data:: STD_OUTPUT_HANDLE
+ 
+    The standard output device. Initially, this is the active console screen
+    buffer, ``CONOUT$``.
+ 
+ .. data:: STD_ERROR_HANDLE
+ 
+    The standard error device. Initially, this is the active console screen
+    buffer, ``CONOUT$``.
+ 
+ .. data:: SW_HIDE
+ 
+    Hides the window. Another window will be activated.
+ 
+ .. data:: STARTF_USESTDHANDLES
+ 
+    Specifies that the :attr:`STARTUPINFO.hStdInput`,
+    :attr:`STARTUPINFO.hStdOutput`, and :attr:`STARTUPINFO.hStdError` members
+    contain additional information.
+ 
+ .. data:: STARTF_USESHOWWINDOW
+ 
+    Specifies that the :attr:`STARTUPINFO.wShowWindow` member contains
+    additional information.
+ 
+ .. data:: CREATE_NEW_CONSOLE
+ 
+    The new process has a new console, instead of inheriting its parent's
+    console (the default).
+ 
+    This flag is always set when :class:`Popen` is created with ``shell=True``.
+ 
++.. data:: CREATE_NEW_PROCESS_GROUP
++
++   A :class:`Popen` ``creationflags`` parameter to specify that a new process
++   group will be created. This flag is necessary for using :func:`os.kill`
++   on the subprocess.
++
++   This flag is ignored if :data:`CREATE_NEW_CONSOLE` is specified.
++
+ 
  .. _subprocess-replacements:
  
  Replacing Older Functions with the subprocess Module