It now reads: ...be aware that Python has no control over...
(cherry picked from commit 517da1e5)
Co-authored-by: Alexey <forestbiiird@gmail.com>

Fix a rare but potential pre-exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process.  This bug appears to have been introduced in 3.4 with the inheritable file descriptors support.

This also changes Python/fileutils.c `set_inheritable` to use the "slow" two `fcntl` syscall path instead of the "fast" single `ioctl` syscall path when asked to be async signal safe (by way of being asked not to raise exceptions).  `ioctl` is not a POSIX async-signal-safe approved function.

ref: http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html
(cherry picked from commit c1e46e94)
Co-authored-by: Alexey Izbyshev <izbyshev@users.noreply.github.com>

glibc is deprecating libcrypt in favor of libxcrypt, however python assumes
that crypt.h will always be included. This change makes the header inclusion
explicit when libxcrypt is present on the system.
(cherry picked from commit e768c86e)

On FreeBSD and Solaris, os.strerror() now always decode the byte
string from the current locale encoding, rather than using
ASCII/surrogateescape in some cases.

Changes:

* Add _Py_DecodeLocaleEx() and _Py_EncodeLocaleEx() which has an
  additional current_locale parameter.
* PyUnicode_DecodeLocale(), PyUnicode_DecodeLocaleAndSize() and
* PyUnicode_EncodeLocale() now always use the current locale
* encoding, instead of using Py_DecodeLocale()/Py_EncodeLocale().
* Document encoding in Py_DecodeLocale() and Py_EncodeLocale()
  documentations.
* Add USE_FORCE_ASCII define to not define
  decode_ascii_surrogateescape() on Android.

* Add _Py_GetLocaleconvNumeric() function: decode decimal_point and
  thousands_sep fields of localeconv() from the LC_NUMERIC encoding,
  rather than decoding from the LC_CTYPE encoding.
* Modify locale.localeconv() and "n" formatter of str.format() (for
  int, float and complex to use _Py_GetLocaleconvNumeric()
  internally.

(cherry picked from commit cb064fc2)

(cherry picked from commit 1b3029ac)

(cherry picked from commit 01ae58d4)

Modify the code to use ncurses is_pad() instead of checking WINDOW
_flags field.  If your platform does not provide the is_pad(), the
existing way that checks the field will be enabled.

Note: This change does not drop support for platforms where do not
have both WINDOW _flags field and is_pad().
(cherry picked from commit 8bc7d635)

(cherry picked from commit baac01e6)

(cherry picked from commit 56d1f5ca)

[3.6] bpo-31786: Make functions in the select module blocking when timeout is a small negative value. (GH-4003). (#4022)

(cherry picked from commit 2c15b29a)

(cherry picked from commit a853a8ba)

FreeBSD is the only platforms with unsigned FD_SETSIZE.

(cherry picked from commit 783d0c1a)

* [3.6] bpo-30703: Improve signal delivery (GH-2415)

* Improve signal delivery

Avoid using Py_AddPendingCall from signal handler, to avoid calling signal-unsafe functions.

* Remove unused function

* Improve comments

* Add stress test

* Adapt for --without-threads

* Add second stress test

* Add NEWS blurb

* Address comments @haypo.
(cherry picked from commit c08177a1)

* bpo-30796: Fix failures in signal delivery stress test (#2488)

* bpo-30796: Fix failures in signal delivery stress test

setitimer() can have a poor minimum resolution on some machines,
this would make the test reach its deadline (and a stray signal
could then kill a subsequent test).

* Make sure to clear the itimer after the test

Based on patch by Victor Stinner.

Add private C API function _PyUnicode_AsUnicode() which is similar to
PyUnicode_AsUnicode(), but checks for null characters..
(cherry picked from commit f7eae0ad)

Raise a ValueError if the second argument is NULL and the wchar_t\*
string contains null characters..
(cherry picked from commit e613e6ad)

Replace __PyCodeExtraState_Get() with __PyCodeExtraState_Get(void) to
fix the following GCC warning:

./Include/pystate.h:63:1: warning: function declaration isn't a prototype [-Wstrict-prototypes]
 __PyCodeExtraState* __PyCodeExtraState_Get();

* Move co_extra_freefuncs to interpreter state to avoid crashes in
multi-threaded scenarios involving deletion of code objects

* Don't require that extra be zero initialized

* Build test list instead of defining empty test class

* Ensure extra is always assigned on success

* Keep the old fields in the thread state object, just don't use them
Add new linked list of code extra objects on a per-interpreter basis
  so that interpreter state size isn't changed

* Rename __PyCodeExtraState_Get and add comment about it going away in 3.7
Fix sort order of import's in test_code.py

* Remove an extraneous space

* Remove docstrings for comments

* Touch up formatting

* Fix casing of coextra local

* Fix casing of another variable

* Prefix PyCodeExtraState with __ to match C API for getting it

* Update NEWS file for bpo-30604

* bpo-29259: Remove unused func parameter of _PyStack_UnpackDict()
* bpo-29286: Change _PyStack_UnpackDict() prototype to be able to
  notify of failure when args is NULL. _PyStack_UnpackDict() now
  returns -1 on error.

if Py_LIMITED_API is not defined.
(cherry picked from commit 49a90595)

Make a non-Py_DEBUG, asserts-enabled build of CPython possible. This means
making sure helper functions are defined when NDEBUG is not defined, not
just when Py_DEBUG is defined.

Also fix a division-by-zero in obmalloc.c that went unnoticed because in
Py_DEBUG mode, elsize is never zero.

(cherry picked from commit a00c3fd1 and 06bb4873)

when pass indices of wrong type.
(cherry picked from commit d4edfc9a)