merge 3.3 (#17811)

diff --cc Doc/library/os.rst
index 32c1563f7a1e5ea34bc2ad1fe2e90f13b1e578e9,b11098e95f977856edf18b9b246f61a9ab069e6c..1fc8de96c6ac2861b8271b5ff956e1286296c1fd
--- 1/Doc/library/os.rst
--- 2/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@@ -1103,10 -1019,13 +1103,13 @@@ or `the MSDN <http://msdn.microsoft.com
  
  .. function:: readv(fd, buffers)
  
-    Read from a file descriptor into a number of writable buffers. *buffers* is
-    an arbitrary sequence of writable buffers. Returns the total number of bytes
-    read.
+    Read from a file descriptor *fd* into a number of mutable :term:`bytes-like
+    objects <bytes-like object>` *buffers*. :func:`~os.readv` will transfer data
+    into each buffer until it is full and then move on to the next buffer in the
+    sequence to hold the rest of the data. :func:`~os.readv` returns the total
+    number of bytes read (which may be less than the total capacity of all the
+    objects).
 -          
 +
     Availability: Unix.
  
     .. versionadded:: 3.3
@@@ -1155,11 -1074,84 +1158,12 @@@
  
  .. function:: writev(fd, buffers)
  
-    Write the contents of *buffers* to file descriptor *fd*, where *buffers*
-    is an arbitrary sequence of buffers.
-    Returns the total number of bytes written.
+    Write the contents of *buffers* to file descriptor *fd*. *buffers* must be a
+    sequence of :term:`bytes-like objects <bytes-like object>`.
+    :func:`~os.writev` writes the contents of each object to the file descriptor
+    and returns the total number of bytes written.
 -   
 -   Availability: Unix.
 -
 -   .. versionadded:: 3.3
 -
 -
 -.. _open-constants:
 -
 -``open()`` flag constants
 -~~~~~~~~~~~~~~~~~~~~~~~~~
 -
 -The following constants are options for the *flags* parameter to the
 -:func:`~os.open` function.  They can be combined using the bitwise OR operator
 -``|``.  Some of them are not available on all platforms.  For descriptions of
 -their availability and use, consult the :manpage:`open(2)` manual page on Unix
 -or `the MSDN <http://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windows.
 -
 -
 -.. data:: O_RDONLY
 -          O_WRONLY
 -          O_RDWR
 -          O_APPEND
 -          O_CREAT
 -          O_EXCL
 -          O_TRUNC
 -
 -   These constants are available on Unix and Windows.
 -
 -
 -.. data:: O_DSYNC
 -          O_RSYNC
 -          O_SYNC
 -          O_NDELAY
 -          O_NONBLOCK
 -          O_NOCTTY
 -          O_SHLOCK
 -          O_EXLOCK
 -          O_CLOEXEC
 -
 -   These constants are only available on Unix.
 -
 -   .. versionchanged:: 3.3
 -      Add :data:`O_CLOEXEC` constant.
  
 -.. data:: O_BINARY
 -          O_NOINHERIT
 -          O_SHORT_LIVED
 -          O_TEMPORARY
 -          O_RANDOM
 -          O_SEQUENTIAL
 -          O_TEXT
 -
 -   These constants are only available on Windows.
 -
 -
 -.. data:: O_ASYNC
 -          O_DIRECT
 -          O_DIRECTORY
 -          O_NOFOLLOW
 -          O_NOATIME
 -
 -   These constants are GNU extensions and not present if they are not defined by
 -   the C library.
 -
 -
 -.. data:: RTLD_LAZY
 -          RTLD_NOW
 -          RTLD_GLOBAL
 -          RTLD_LOCAL
 -          RTLD_NODELETE
 -          RTLD_NOLOAD
 -          RTLD_DEEPBIND
 -
 -   See the Unix manual page :manpage:`dlopen(3)`.
 +   Availability: Unix.
  
     .. versionadded:: 3.3
  

diff --cc Modules/posixmodule.c
Simple merge