diff --git a/Doc/library/codecs.rst b/Doc/library/codecs.rst
index 0d38253cd25..e80fc3a33d2 100644
--- a/Doc/library/codecs.rst
+++ b/Doc/library/codecs.rst
@@ -78,7 +78,11 @@ It defines the following functions:
      reference (for encoding only)
    * ``'backslashreplace'``: replace with backslashed escape sequences (for
      encoding only)
-   * ``'surrogateescape'``: replace with surrogate U+DCxx, see :pep:`383`
+   * ``'surrogateescape'``: on decoding, replace with code points in the Unicode
+     Private Use Area ranging from U+DC80 to U+DCFF.  These private code
+     points will then be turned back into the same bytes when the
+     ``surrogateescape`` error handler is used when encoding the data.
+     (See :pep:`383` for more.)
 
    as well as any other error handling name defined via :func:`register_error`.
 
diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index 3059e178152..04fb95ee2f4 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -895,16 +895,36 @@ are always available.  They are listed here in alphabetical order.
    the list of supported encodings.
 
    *errors* is an optional string that specifies how encoding and decoding
-   errors are to be handled--this cannot be used in binary mode.  Pass
-   ``'strict'`` to raise a :exc:`ValueError` exception if there is an encoding
-   error (the default of ``None`` has the same effect), or pass ``'ignore'`` to
-   ignore errors.  (Note that ignoring encoding errors can lead to data loss.)
-   ``'replace'`` causes a replacement marker (such as ``'?'``) to be inserted
-   where there is malformed data.  When writing, ``'xmlcharrefreplace'``
-   (replace with the appropriate XML character reference) or
-   ``'backslashreplace'`` (replace with backslashed escape sequences) can be
-   used.  Any other error handling name that has been registered with
-   :func:`codecs.register_error` is also valid.
+   errors are to be handled--this cannot be used in binary mode.
+   A variety of standard error handlers are available, though any
+   error handling name that has been registered with
+   :func:`codecs.register_error` is also valid.  The standard names
+   are:
+
+   * ``'strict'`` to raise a :exc:`ValueError` exception if there is
+     an encoding error.  The default value of ``None`` has the same
+     effect.
+
+   * ``'ignore'`` ignores errors.  Note that ignoring encoding errors
+     can lead to data loss.
+
+   * ``'replace'`` causes a replacement marker (such as ``'?'``) to be inserted
+     where there is malformed data.
+
+   * ``'surrogateescape'`` will represent any incorrect bytes as code
+     points in the Unicode Private Use Area ranging from U+DC80 to
+     U+DCFF.  These private code points will then be turned back into
+     the same bytes when the ``surrogateescape`` error handler is used
+     when writing data.  This is useful for processing files in an
+     unknown encoding.
+
+   * ``'xmlcharrefreplace'`` is only supported when writing to a file.
+     Characters not supported by the encoding are replaced with the
+     appropriate XML character reference ``&#nnn;``.
+
+   * ``'backslashreplace'`` (also only supported when writing)
+     replaces unsupported characters with Python's backslashed escape
+     sequences.
 
    .. index::
       single: universal newlines; open() built-in function
diff --git a/Lib/codecs.py b/Lib/codecs.py
index 48d4c9c7395..6a6eb900c72 100644
--- a/Lib/codecs.py
+++ b/Lib/codecs.py
@@ -105,6 +105,7 @@ class Codec:
                     Python will use the official U+FFFD REPLACEMENT
                     CHARACTER for the builtin Unicode codecs on
                     decoding and '?' on encoding.
+         'surrogateescape' - replace with private codepoints U+DCnn.
          'xmlcharrefreplace' - Replace with the appropriate XML
                                character reference (only for encoding).
          'backslashreplace'  - Replace with backslashed escape sequences
diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index 689046ebbff..a62d9a455fe 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -810,6 +810,7 @@ class Popen(object):
             if universal_newlines:
                 self.stderr = io.TextIOWrapper(self.stderr)
 
+        self._closed_child_pipe_fds = False
         try:
             self._execute_child(args, executable, preexec_fn, close_fds,
                                 pass_fds, cwd, env,
@@ -826,19 +827,21 @@ class Popen(object):
                 except EnvironmentError:
                     pass  # Ignore EBADF or other errors.
 
-            # Make sure the child pipes are closed as well.
-            to_close = []
-            if stdin == PIPE:
-                to_close.append(p2cread)
-            if stdout == PIPE:
-                to_close.append(c2pwrite)
-            if stderr == PIPE:
-                to_close.append(errwrite)
-            for fd in to_close:
-                try:
-                    os.close(fd)
-                except EnvironmentError:
-                    pass
+            if not self._closed_child_pipe_fds:
+                to_close = []
+                if stdin == PIPE:
+                    to_close.append(p2cread)
+                if stdout == PIPE:
+                    to_close.append(c2pwrite)
+                if stderr == PIPE:
+                    to_close.append(errwrite)
+                if hasattr(self, '_devnull'):
+                    to_close.append(self._devnull)
+                for fd in to_close:
+                    try:
+                        os.close(fd)
+                    except EnvironmentError:
+                        pass
 
             raise
 
@@ -1383,14 +1386,18 @@ class Popen(object):
                     # be sure the FD is closed no matter what
                     os.close(errpipe_write)
 
-                if p2cread != -1 and p2cwrite != -1:
+                # self._devnull is not always defined.
+                devnull_fd = getattr(self, '_devnull', None)
+                if p2cread != -1 and p2cwrite != -1 and p2cread != devnull_fd:
                     os.close(p2cread)
-                if c2pwrite != -1 and c2pread != -1:
+                if c2pwrite != -1 and c2pread != -1 and c2pwrite != devnull_fd:
                     os.close(c2pwrite)
-                if errwrite != -1 and errread != -1:
+                if errwrite != -1 and errread != -1 and errwrite != devnull_fd:
                     os.close(errwrite)
-                if hasattr(self, '_devnull'):
-                    os.close(self._devnull)
+                if devnull_fd is not None:
+                    os.close(devnull_fd)
+                # Prevent a double close of these fds from __init__ on error.
+                self._closed_child_pipe_fds = True
 
                 # Wait for exec to fail or succeed; possibly raising an
                 # exception (limited in size)
diff --git a/Lib/test/test_curses.py b/Lib/test/test_curses.py
index e959622c733..76812b71ba3 100644
--- a/Lib/test/test_curses.py
+++ b/Lib/test/test_curses.py
@@ -252,6 +252,18 @@ def test_userptr_without_set(stdscr):
     except curses.panel.error:
         pass
 
+def test_userptr_memory_leak(stdscr):
+    w = curses.newwin(10, 10)
+    p = curses.panel.new_panel(w)
+    obj = object()
+    nrefs = sys.getrefcount(obj)
+    for i in range(100):
+        p.set_userptr(obj)
+
+    p.set_userptr(None)
+    if sys.getrefcount(obj) != nrefs:
+        raise RuntimeError("set_userptr leaked references")
+
 def test_resize_term(stdscr):
     if hasattr(curses, 'resizeterm'):
         lines, cols = curses.LINES, curses.COLS
@@ -317,6 +329,7 @@ def main(stdscr):
         module_funcs(stdscr)
         window_funcs(stdscr)
         test_userptr_without_set(stdscr)
+        test_userptr_memory_leak(stdscr)
         test_resize_term(stdscr)
         test_issue6243(stdscr)
         test_unget_wch(stdscr)
diff --git a/Misc/NEWS b/Misc/NEWS
index 70b183f7931..67bc8dc6b9f 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -32,6 +32,10 @@ Core and Builtins
 Library
 -------
 
+- subprocess: Prevent a possible double close of parent pipe fds when the
+  subprocess exec runs into an error.  Prevent a regular multi-close of the
+  /dev/null fd when any of stdin, stdout and stderr was set to DEVNULL.
+
 - Issue #16102: Make uuid._netbios_getnode() work again on Python 3.
 
 - Issue #18109: os.uname() now decodes fields from the locale encoding, and
@@ -78,6 +82,9 @@ Library
   the default for linking if LDSHARED is not also overriden.  This restores
   Distutils behavior introduced in 3.2.3 and inadvertently dropped in 3.3.0.
 
+- Issue #18113: Fixed a refcount leak in the curses.panel module's
+  set_userptr() method.  Reported by Atsuo Ishimoto.
+
 IDLE
 ----
 
diff --git a/Modules/_curses_panel.c b/Modules/_curses_panel.c
index 1c7d0842e84..c11f3d84768 100644
--- a/Modules/_curses_panel.c
+++ b/Modules/_curses_panel.c
@@ -322,6 +322,10 @@ PyCursesPanel_replace_panel(PyCursesPanelObject *self, PyObject *args)
 static PyObject *
 PyCursesPanel_set_panel_userptr(PyCursesPanelObject *self, PyObject *obj)
 {
+    PyObject *oldobj;
+    PyCursesInitialised;
+    oldobj = (PyObject *) panel_userptr(self->pan);
+    Py_XDECREF(oldobj);
     Py_INCREF(obj);
     return PyCursesCheckERR(set_panel_userptr(self->pan, (void*)obj),
                             "set_panel_userptr");
diff --git a/Modules/_io/_iomodule.c b/Modules/_io/_iomodule.c
index b5cd1769d4f..4a7e758cda5 100644
--- a/Modules/_io/_iomodule.c
+++ b/Modules/_io/_iomodule.c
@@ -168,8 +168,8 @@ PyDoc_STRVAR(open_doc,
 "'strict' to raise a ValueError exception if there is an encoding error\n"
 "(the default of None has the same effect), or pass 'ignore' to ignore\n"
 "errors. (Note that ignoring encoding errors can lead to data loss.)\n"
-"See the documentation for codecs.register for a list of the permitted\n"
-"encoding error strings.\n"
+"See the documentation for codecs.register or run 'help(codecs.Codec)'\n"
+"for a list of the permitted encoding error strings.\n"
 "\n"
 "newline controls how universal newlines works (it only applies to text\n"
 "mode). It can be None, '', '\\n', '\\r', and '\\r\\n'.  It works as\n"
diff --git a/Modules/_io/textio.c b/Modules/_io/textio.c
index cff9c6e9372..cd751c14003 100644
--- a/Modules/_io/textio.c
+++ b/Modules/_io/textio.c
@@ -642,8 +642,9 @@ PyDoc_STRVAR(textiowrapper_doc,
     "encoding gives the name of the encoding that the stream will be\n"
     "decoded or encoded with. It defaults to locale.getpreferredencoding(False).\n"
     "\n"
-    "errors determines the strictness of encoding and decoding (see the\n"
-    "codecs.register) and defaults to \"strict\".\n"
+    "errors determines the strictness of encoding and decoding (see\n"
+    "help(codecs.Codec) or the documentation for codecs.register) and\n"
+    "defaults to \"strict\".\n"
     "\n"
     "newline controls how line endings are handled. It can be None, '',\n"
     "'\\n', '\\r', and '\\r\\n'.  It works as follows:\n"