Based on patch by Victor Stinner.

Add private C API function _PyUnicode_AsUnicode() which is similar to
PyUnicode_AsUnicode(), but checks for null characters.

bpo-29619: os.stat() and os.DirEntry.inodeo() now convert inode
(st_ino) using unsigned integers.

to/from UTF-8, instead of the locale encoding to avoid inconsistencies with
os.fsencode() and os.fsdecode() which are already using UTF-8.

that do not have the ioctl FIOCLEX and FIONCLEX commands

Issue #27938: Normalize aliases of the ASCII encoding, because
_Py_normalize_encoding() now correctly normalize encoding names.

Most fixes to Doc/ and Lib/ directories by Ville Skyttä.

Issue #27057: Fix os.set_inheritable() on Android, ioctl() is blocked by
SELinux and fails with EACCESS. The function now falls back to fcntl().

Patch written by Michał Bednarski.

Issue #26770: set_inheritable() avoids calling fcntl() twice if the FD_CLOEXEC
is already set/cleared. This change only impacts platforms using the fcntl()
implementation of set_inheritable() (not Linux nor Windows).

Issue #10915, #15751, #26558:

* PyGILState_Check() now returns 1 (success) before the creation of the GIL and
  after the destruction of the GIL. It allows to use the function early in
  Python initialization and late in Python finalization.
* Add a flag to disable PyGILState_Check(). Disable PyGILState_Check() when
  Py_NewInterpreter() is called
* Add assert(PyGILState_Check()) to: _Py_dup(), _Py_fstat(), _Py_read()
  and _Py_write()

Add "#ifdef WITH_THREAD" around cals to:

* PyGILState_Check()
* _PyImport_AcquireLock()
* _PyImport_ReleaseLock()

Add "#ifdef WITH_THREAD" around cals to:

* PyGILState_Check()
* _PyImport_AcquireLock()
* _PyImport_ReleaseLock()

Issue #23524: Replace _PyVerify_fd function with calls to _set_thread_local_invalid_parameter_handler.

Helper to write() which retries write() if it is interrupted by a signal (fails
with EINTR).

Add _Py_fstat_noraise() function when a Python exception is not welcome.

I expected more users of _Py_wstat(), but in practice it's only used by
Modules/getpath.c. Move the function because it's not needed on Windows.
Windows uses PC/getpathp.c which uses the Win32 API (ex: GetFileAttributesW())
not the POSIX API.

fstat(), these functions are always required.

Remove HAVE_STAT and HAVE_FSTAT defines, and stop supporting DONT_HAVE_STAT and
DONT_HAVE_FSTAT.

Save and then restore errno because PyErr_CheckSignals() and
PyErr_SetFromErrno() can modify it.

_Py_write() to know which test failed on the buildbot "AMD64 Snow Leop 3.x".

Fix typo: self->fd => fd

EINTR error and special cases for Windows.

These functions now truncate the length to PY_SSIZE_T_MAX to have a portable
and reliable behaviour. For example, read() result is undefined if counter is
greater than PY_SSIZE_T_MAX on Linux.

Retry open()/fopen() if it fails with EINTR and the Python signal handler
doesn't raise an exception.

* If fopen() fails, OSError is raised with the original filename object.
* The GIL is now released while calling fopen()

* _Py_open() now raises exceptions on error. If open() fails, it raises an
  OSError with the filename.
* _Py_open() now releases the GIL while calling open()
* Add _Py_open_noraise() when _Py_open() cannot be used because the GIL is not
  held

Issue #23524: Replace _PyVerify_fd function with calling _set_thread_local_invalid_parameter_handler on every thread.

Issue #23152: Renames time_t_to_FILE_TIME to _Py_time_t_to_FILE_TIME, removes unused struct win32_stat and return value

fstat() may fail with EOVERFLOW on files larger than 2 GB because the file size type is an signed 32-bit integer.

This platform exposes the function ioctl(FIOCLEX), but calling it fails with
errno is ENOTTY: "Inappropriate ioctl for device". set_inheritable() now falls
back to the slower fcntl() (F_GETFD and then F_SETFD).

``_Py_wchar2char()`` to :c:func:`Py_EncodeLocale`, and document these
functions.

set the blocking mode of a file descriptor (False if the O_NONBLOCK flag is
set, True otherwise). These functions are not available on Windows.

PATH_MAX is not declared on IRIX nor Windows.