bpo-34523, bpo-35290: C locale coercion now resets the Python
internal "force ASCII" mode. This change fix the filesystem encoding
on FreeBSD CURRENT, which has a new "C.UTF-8" locale, when
the UTF-8 mode is disabled.

Add _Py_ResetForceASCII(): _Py_SetLocaleFromEnv() now calls it.

Add pycore_fileutils.h and pycore_object.h to Makefile.pre.in and to
the pythoncore project of PCbuild/.

Partially revert commit 5f2df88b:
add "#undef Yield" to .c files after including Python-ast.h.

Fix the warning:

    winbase.h(102): warning C4005: 'Yield': macro redefinition

If _PyObject_Dump() detects that the object is freed, don't try to
dump it (exit immediately).

Enhance also _PyObject_IsFreed(): it now detects if the pointer
itself looks like freed memory.

os_read_impl() now also truncates the size to _PY_READ_MAX
on macOS, to avoid to allocate a larger buffer even if _Py_read() is
limited to _PY_READ_MAX bytes (ex: INT_MAX on macOS).

When iterating using asdl_seq_LEN(), use 'Py_ssize_t' type instead of
'int' for the iterator variable, to avoid downcast on 64-bit platforms.

_Py_asdl_int_seq_new() now also ensures that the index is greater than
or equal to 0.

CryptGenRandom() maximum size is PY_DWORD_MAX, not INT_MAX.
Use DWORD type for the 'chunk' variable
Co-Authored-By: Jeremy Kloth <jeremy.kloth@gmail.com>

Explicit cast a pointer difference (intptr_t) to int to fix
two warnings on 64-bit Windows:

    Modules\pyexpat.c(1181): warning C4244: 'initializing':
    conversion from '__int64' to 'int', possible  loss of data

    Modules\pyexpat.c(1192): warning C4244: 'initializing':
    conversion from '__int64' to 'int', possible  loss of data

Fixed the following compiler warning in multibytecodec.c:

    warning C4244: '=': conversion from 'Py_ssize_t'
    to 'unsigned char', possible loss of data

Cast Py_ssize_t to unsigned char: the maximum value is checked
on the previous line.

Don't pass void* to Python macros: use _PyObject_CAST().

Don't pass complex expressions but regular variables to Python
macros.

* _datetimemodule.c: split single large "if" into two "if"
  in date_new(), time_new() and datetime_new().
* _pickle.c, load_extension(): flatten complex "if" expression into
  more regular C code.
* _ssl.c: addbool() now uses a temporary bool_obj to only evaluate
  the value once.
* weakrefobject.c: replace "Py_INCREF(result = proxy);"
  with "result = proxy; Py_INCREF(result);"

Add _PyObject_CAST() and _PyVarObject_CAST() macros to cast argument
to PyObject* and PyVarObject* properly.

* Add _PyObject_ASSERT_FROM() and _PyObject_ASSERT_FAILED_MSG()
  macros.
* PyObject_GC_Track() now calls _PyObject_ASSERT_FAILED_MSG(),
  instead of Py_FatalError(), if the object is already tracked, to
  dump more information on error.
* _PyObject_GC_TRACK() no longer checks if the object is already
  tracked at runtime, use an assertion instead for best performances;
  PyObject_GC_Track() still checks at runtime.
* pycore_object.h now includes pycore_pystate.h.
* Convert _PyObject_GC_TRACK() and _PyObject_GC_UNTRACK() macros to
  inline functions.

Enhance _PyObject_AssertFailed()

* Exchange 'expr' and 'msg' parameters
* 'expr' and 'func' arguments can now be NULL

Move _PyObject_GC_TRACK() and _PyObject_GC_UNTRACK() from
Include/objimpl.h to Include/internal/pycore_object.h.

Call setitimer() before each test method, instead of once per test
case, to ensure that signals are sent in each test method.
Previously, only the first method of a testcase class got signals.

Changes:

* Replace setUpClass() with setUp() and replace tearDownClass() with
  tearDown().
* tearDown() now ensures that at least one signal has been sent.
* Replace support.run_unittest() with unittest.main() which has
  a nicer CLI and automatically discover test cases.

I'll watch for 404 on the old URL and will setup an HTTP redirection if needed.

In verbose mode, test_c_locale_coercion now dumps global variables at
startup.

Partially revert commit 1a6be91e,
move back PyGC API from the internal API to the C API:

* _PyGCHead_NEXT(g), _PyGCHead_SET_NEXT(g, p)
* _PyGCHead_PREV(g), _PyGCHead_SET_PREV(g, p)
* _PyGCHead_FINALIZED(g), _PyGCHead_SET_FINALIZED(g)
* _PyGC_FINALIZED(o), _PyGC_SET_FINALIZED(o)
* _PyGC_PREV_MASK_FINALIZED
* _PyGC_PREV_MASK_COLLECTING
* _PyGC_PREV_SHIFT
* _PyGC_PREV_MASK

_PyObject_GC_TRACK(o) and _PyObject_GC_UNTRACK(o) remain in the
internal API.

Fixes assertion failures in _datetimemodule.c
introduced in the previous fix (see bpo-31752).

Rather of trying to handle an int subclass as exact int,
let it to use overridden special methods, but check the
result of divmod().

locale.localeconv() now sets temporarily the LC_CTYPE locale to the
LC_MONETARY locale if the two locales are different and monetary
strings are non-ASCII. This temporary change affects other threads.

Changes:

* locale.localeconv() can now set LC_CTYPE to LC_MONETARY to decode
  monetary fields.
* Add LocaleInfo.grouping_buffer: copy localeconv() grouping string
  since it can be replaced anytime if a different thread calls
  localeconv().
* _Py_GetLocaleconvNumeric() now requires a "struct lconv *"
  structure, so locale.localeconv() now longer calls localeconv()
  twice. Moreover, the function now requires all arguments to be
  non-NULL.
* Rename STATIC_LOCALE_INFO_INIT to LocaleInfo_STATIC_INIT.
* Move _Py_GetLocaleconvNumeric() definition from fileutils.h
  to pycore_fileutils.h. pycore_fileutils.h now includes locale.h.
* The _locale module is now built with Py_BUILD_CORE defined.

coro->cr_origin wasn't initialized if compute_cr_origin() failed in
PyCoro_New(), which would cause a crash during the coroutine's
deallocation.



https://bugs.python.org/issue35269

Source of T_STRING: https://github.com/python/cpython/blob/e42b705188271da108de42b55d9344642170aa2b/Python/structmember.c#L51

Source of PyUnicode_FromString
https://github.com/python/cpython/blob/master/Include/unicodeobject.h#L702


https://bugs.python.org/issue25438

[Issue 28401](https://bugs.python.org/issue28401): Don't attempt to import the stable API extensions, they are not supported in PyDEBUG builds (which don't implement that ABI).


https://bugs.python.org/issue28401

This missed PyErr_NoMemory() could cause a SystemError when calling
_symtable.symtable().