* Fix handshake timeout leak in asyncio/sslproto

Refs MagicStack/uvloop#222

* Break circular ref _SSLPipe <-> SSLProtocol

* bpo-34745: Fix asyncio ssl memory leak

* Break circular ref SSLProtocol <-> UserProtocol

* Add NEWS entry

bpo-35493: Use Process.sentinel instead of sleeping for polling worker status in multiprocessing.Pool (#11488)

* bpo-35493: Use Process.sentinel instead of sleeping for polling worker status in multiprocessing.Pool

* Use self-pipe pattern to avoid polling for changes

* Refactor some variable names and add comments

* Restore timeout and poll

* Use reader object only on wait()

* Recompute worker sentinels every time

* Remove timeout and use change notifier

* Refactor some methods to be overloaded by the ThreadPool, document the cache class and fix typos

ProcessPoolExecutor workers will hold the return value of their last task in memory until the next task is received. Since the return value has already been propagated to the parent process's Future (or has been discarded by this point), the object can be safely released.

* Replace external recipe link with a link to the dataclasses module.

* Highlight the class definition syntax for typing.NamedTuple
  and add an example for clarity.

Be explicit that timedelta division converts an overall duration to the interval
units given by the denominator.

The function has no return value.

Fix the following warning on Windows:

    python\ceval.c(180): warning C4098: 'PyEval_InitThreads':
    'void' function returning a value

If argv is empty, add an empty string.

Replace messy _Py_wstrlist_xxx() functions with a new clean
_PyWstrList structure and new _PyWstrList_xxx() functions.

Changes:

* Add _PyCoreConfig.use_module_search_paths to decide if
  _PyCoreConfig.module_search_paths should be computed or not, to
  support empty search path list.
* _PyWstrList_Clear() sets length to 0 and items to NULL, whereas
  _Py_wstrlist_clear() only freed memory.
* _PyWstrList_Append() returns an int, whereas _Py_wstrlist_append()
  returned _PyInitError.
* _PyWstrList uses Py_ssize_t for the length, instead of int.
* Replace (int, wchar_t**) with _PyWstrList in:

  * _PyPreConfig
  * _PyCoreConfig
  * _PyPreCmdline
  * _PyCmdline

* Replace "int orig_argv; wchar_t **orig_argv;"
  with "_PyWstrList orig_argv".
* _PyCmdline and _PyPreCmdline now also copy wchar_argv.
* Rename _PyArgv_Decode() to _PyArgv_AsWstrList().
* PySys_SetArgvEx() now pass the fixed (argc, argv) to
  _PyPathConfig_ComputeArgv0() (don't pass negative argc or NULL
  argv).
* _PyOS_GetOpt() uses Py_ssize_t

Fix CFLAGS in customize_compiler() of distutils.sysconfig: when the
CFLAGS environment variable is defined, don't override CFLAGS variable with
the OPT variable anymore.

Initial patch written by David Malcolm.
Co-Authored-By: David Malcolm <dmalcolm@redhat.com>

This optimization is not only for space, but also for speed.

The value is a string for string and byte literals, None otherwise.
It is 'u' for u"..." literals, 'b' for b"..." literals, '' for "..." literals.
The 'r' (raw) prefix is ignored.
Does not apply to f-strings.

This appears sufficient to make mypy capable of using the stdlib ast module instead of typed_ast (assuming a mypy patch I'm working on).

WIP: I need to make the tests pass. @ilevkivskyi @serhiy-storchaka 



https://bugs.python.org/issue36280

Limited signal fields in VxWorks.

Fix an unlikely memory leak on conversion from string to float in the
function _Py_dg_strtod() used by float(str), complex(str),
pickle.load(), marshal.load(), etc.

Fix an unlikely memory leak in _Py_dg_strtod() on "undfl:" label:
rewrite memory management in this function to always release all
memory before exiting the function. Initialize variables to NULL, and
set them to NULL after calling Bfree() at the "cont:" label.

Note: Bfree(NULL) is well defined: it does nothing.

Sizeof new empty dict becomes 72 bytes from 240 bytes (amd64).
It is same size to empty dict created by dict.clear().