Misc/NEWS.d/3.11.0a2.rst

.. bpo: 45716
.. date: 2021-11-04-20-19-07
.. nonce: 5C0pA1
.. release date: 2021-11-05
.. section: Core and Builtins

Improve the :exc:`SyntaxError` message when using ``True``, ``None`` or
``False`` as keywords in a function call. Patch by Pablo Galindo.

..

.. bpo: 45688
.. date: 2021-11-02-09-27-46
.. nonce: v5Der1
.. section: Core and Builtins

:data:`sys.stdlib_module_names` now contains the macOS-specific module
:mod:`_scproxy`.

..

.. bpo: 45379
.. date: 2021-10-23-13-49-00
.. nonce: ZF7G3n
.. section: Core and Builtins

Clarify :exc:`ImportError` message when we try to explicitly import a frozen
module but frozen modules are disabled.

..

.. bpo: 44525
.. date: 2021-10-20-11-57-31
.. nonce: veL4lJ
.. section: Core and Builtins

Specialize simple calls to Python functions (no starargs, keyowrd dict, or
closure)

..

.. bpo: 45530
.. date: 2021-10-20-01-28-26
.. nonce: 5r7n4m
.. section: Core and Builtins

Cases of sorting using tuples as keys may now be significantly faster in
some cases. Patch by Tim Peters.

The order of the result may differ from earlier releases if the tuple
elements don't define a total ordering (see
:ref:`expressions-value-comparisons` for information on total ordering).
It's generally true that the result of sorting simply isn't well-defined in
the absence of a total ordering on list elements.

..

.. bpo: 45526
.. date: 2021-10-19-10-29-47
.. nonce: WQnvW9
.. section: Core and Builtins

In obmalloc, set ADDRESS_BITS to not ignore any bits (ignored 16 before).
That is safer in the case that the kernel gives user-space virtual addresses
that span a range greater than 48 bits.

..

.. bpo: 30570
.. date: 2021-10-19-01-04-08
.. nonce: _G30Ms
.. section: Core and Builtins

Fixed a crash in ``issubclass()`` from infinite recursion when searching
pathological ``__bases__`` tuples.

..

.. bpo: 45521
.. date: 2021-10-18-22-40-33
.. nonce: GdMiuW
.. section: Core and Builtins

Fix a bug in the obmalloc radix tree code.  On 64-bit machines, the bug
causes the tree to hold 46-bits of virtual addresses, rather than the
intended 48-bits.

..

.. bpo: 45494
.. date: 2021-10-16-17-27-48
.. nonce: vMt1g4
.. section: Core and Builtins

Fix parser crash when reporting errors involving invalid continuation
characters. Patch by Pablo Galindo.

..

.. bpo: 45445
.. date: 2021-10-12-14-41-39
.. nonce: _F5cMf
.. section: Core and Builtins

Python now fails to initialize if it finds an invalid :option:`-X` option in
the command line. Patch by Pablo Galindo.

..

.. bpo: 45340
.. date: 2021-10-08-09-47-38
.. nonce: ukHgDb
.. section: Core and Builtins

Object attributes are held in an array instead of a dictionary. An object's
dictionary are created lazily, only when needed. Reduces the memory
consumption of a typical Python object by about 30%. Patch by Mark Shannon.

..

.. bpo: 45408
.. date: 2021-10-07-21-26-44
.. nonce: qUqzcd
.. section: Core and Builtins

Fix a crash in the parser when reporting tokenizer errors that occur at the
same time unclosed parentheses are detected. Patch by Pablo Galindo.

..

.. bpo: 29410
.. date: 2021-10-07-19-09-12
.. nonce: bg5SYp
.. section: Core and Builtins

Add SipHash13 for string hash algorithm and use it by default.

..

.. bpo: 45385
.. date: 2021-10-06-21-20-11
.. nonce: CTUT8s
.. section: Core and Builtins

Fix reference leak from descr_check. Patch by Dong-hee Na.

..

.. bpo: 45367
.. date: 2021-10-05-03-49-07
.. nonce: _astoU
.. section: Core and Builtins

Specialized the ``BINARY_MULTIPLY`` opcode to ``BINARY_MULTIPLY_INT`` and
``BINARY_MULTIPLY_FLOAT`` using the PEP 659 machinery.

..

.. bpo: 21736
.. date: 2021-10-01-09-21-02
.. nonce: RI47BU
.. section: Core and Builtins

Frozen stdlib modules now have ``__file__`` to the .py file they would
otherwise be loaded from, if possible.  For packages, ``__path__`` now has
the correct entry instead of being an empty list, which allows unfrozen
submodules to be imported.  These are set only if the stdlib directory is
known when the runtime is initialized.  Note that the file at ``__file__``
is not guaranteed to exist.  None of this affects non-stdlib frozen modules
nor, for now, frozen modules imported using
``PyImport_ImportFrozenModule()``.  Also, at the moment ``co_filename`` is
not updated for the module.

..

.. bpo: 45020
.. date: 2021-10-01-09-06-54
.. nonce: Cj5VQN
.. section: Core and Builtins

For frozen stdlib modules, record the original module name as
``module.__spec__.loader_state.origname``.  If the value is different than
``module.__spec__.name`` then the module was defined as an alias in
Tools/scripts/freeze_modules.py.  If it is ``None`` then the module comes
from a source file outside the stdlib.

..

.. bpo: 45324
.. date: 2021-09-29-12-02-39
.. nonce: BTQElX
.. section: Core and Builtins

In FrozenImporter.find_spec(), we now preserve the information needed in
exec_module() to load the module.  This change mostly impacts internal
details, rather than changing the importer's behavior.

..

.. bpo: 45292
.. date: 2021-09-26-18-18-50
.. nonce: aX5HVr
.. section: Core and Builtins

Implement :pep:`654`. Add :class:`ExceptionGroup` and
:class:`BaseExceptionGroup`. Update traceback display code.

..

.. bpo: 40116
.. date: 2021-09-23-14-00-05
.. nonce: KaoeFs
.. section: Core and Builtins

Change to the implementation of split dictionaries. Classes where the
instances differ either in the exact set of attributes, or in the order in
which those attributes are set, can still share keys. This should have no
observable effect on users of Python or the C-API. Patch by Mark Shannon.

..

.. bpo: 44050
.. date: 2021-09-08-00-30-09
.. nonce: mFI15u
.. section: Core and Builtins

Extensions that indicate they use global state (by setting ``m_size`` to -1)
can again be used in multiple interpreters. This reverts to behavior of
Python 3.8.

..

.. bpo: 44525
.. date: 2021-06-28-22-23-59
.. nonce: sSvUKG
.. section: Core and Builtins

Setup initial specialization infrastructure for the ``CALL_FUNCTION``
opcode. Implemented initial specializations for C function calls:

* ``CALL_FUNCTION_BUILTIN_O`` for ``METH_O`` flag.

* ``CALL_FUNCTION_BUILTIN_FAST`` for ``METH_FASTCALL`` flag without keywords.

* ``CALL_FUNCTION_LEN`` for ``len(o)``.

* ``CALL_FUNCTION_ISINSTANCE`` for ``isinstance(o, t)``.

..

.. bpo: 44511
.. date: 2021-06-26-16-55-08
.. nonce: k8sMvV
.. section: Core and Builtins

Improve the generated bytecode for class and mapping patterns.

..

.. bpo: 43706
.. date: 2021-04-03-02-44-15
.. nonce: jjsXlT
.. section: Core and Builtins

Speed up calls to ``enumerate()`` by using the :pep:`590` ``vectorcall``
calling convention. Patch by Dong-hee Na.

..

.. bpo: 45679
.. date: 2021-10-30-21-11-37
.. nonce: Dq8Cpu
.. section: Library

Fix caching of multi-value :data:`typing.Literal`. ``Literal[True, 2]`` is
no longer equal to ``Literal[1, 2]``.

..

.. bpo: 42064
.. date: 2021-10-27-13-28-52
.. nonce: UK4jgV
.. section: Library

Convert :mod:`sqlite3` to multi-phase initialisation (PEP 489). Patches by
Erlend E. Aasland.

..

.. bpo: 45438
.. date: 2021-10-27-10-05-39
.. nonce: Xz5lGU
.. section: Library

Fix typing.Signature string representation for generic builtin types.

..

.. bpo: 45613
.. date: 2021-10-26-14-29-54
.. nonce: 55Ie3c
.. section: Library

:mod:`sqlite3` now sets :attr:`sqlite3.threadsafety` based on the default
threading mode the underlying SQLite library has been compiled with. Patch
by Erlend E. Aasland.

..

.. bpo: 45574
.. date: 2021-10-22-23-06-33
.. nonce: svqA84
.. section: Library

Fix warning about ``print_escape`` being unused.

..

.. bpo: 45581
.. date: 2021-10-22-21-57-02
.. nonce: rlH6ay
.. section: Library

:meth:`sqlite3.connect` now correctly raises :exc:`MemoryError` if the
underlying SQLite API signals memory error. Patch by Erlend E. Aasland.

..

.. bpo: 45557
.. date: 2021-10-21-16-18-51
.. nonce: 4MQt4r
.. section: Library

pprint.pprint() now handles underscore_numbers correctly. Previously it was
always setting it to False.

..

.. bpo: 44019
.. date: 2021-10-21-10-14-22
.. nonce: Xk4Ncr
.. section: Library

Add :func:`operator.call` to ``operator.__all__``. Patch by Kreusada.

..

.. bpo: 42174
.. date: 2021-10-19-01-30-57
.. nonce: O2w9bi
.. section: Library

:meth:`shutil.get_terminal_size` now falls back to sane values if the column
or line count are 0.

..

.. bpo: 35673
.. date: 2021-10-18-18-12-47
.. nonce: KOkHWe
.. section: Library

Improve the introspectability of the ``__loader__`` attribute for namespace
packages.  :class:`importlib.machinery.NamespaceLoader` is now public, and
implements the :class:`importlib.abc.InspectLoader` interface.
``_NamespaceLoader`` is kept for backward compatibility.

..

.. bpo: 45515
.. date: 2021-10-18-14-52-48
.. nonce: aXdvm_
.. section: Library

Add references to :mod:`zoneinfo` in the :mod:`datetime` documentation,
mostly replacing outdated references to ``dateutil.tz``. Change by Paul
Ganssle.

..

.. bpo: 45475
.. date: 2021-10-18-10-46-47
.. nonce: sb9KDF
.. section: Library

Reverted optimization of iterating :class:`gzip.GzipFile`,
:class:`bz2.BZ2File`, and :class:`lzma.LZMAFile` (see bpo-43787) because it
caused regression when user iterate them without having reference of them.
Patch by Inada Naoki.

..

.. bpo: 45489
.. date: 2021-10-16-23-46-39
.. nonce: QB0rhG
.. section: Library

Update :class:`~typing.ForwardRef` to support ``|`` operator. Patch by
Dong-hee Na.

..

.. bpo: 42222
.. date: 2021-10-15-11-30-11
.. nonce: hdHyac
.. section: Library

Removed deprecated support for float arguments in *randrange()*.

..

.. bpo: 45428
.. date: 2021-10-14-18-04-17
.. nonce: mM2War
.. section: Library

Fix a regression in py_compile when reading filenames from standard input.

..

.. bpo: 45467
.. date: 2021-10-14-13-31-19
.. nonce: Q7Ma6A
.. section: Library

Fix incremental decoder and stream reader in the "raw-unicode-escape" codec.
Previously they failed if the escape sequence was split.

..

.. bpo: 45461
.. date: 2021-10-14-00-19-02
.. nonce: 4LB_tJ
.. section: Library

Fix incremental decoder and stream reader in the "unicode-escape" codec.
Previously they failed if the escape sequence was split.

..

.. bpo: 45239
.. date: 2021-10-13-17-52-48
.. nonce: 7li1_0
.. section: Library

Fixed :func:`email.utils.parsedate_tz` crashing with
:exc:`UnboundLocalError` on certain invalid input instead of returning
``None``. Patch by Ben Hoyt.

..

.. bpo: 45417
.. date: 2021-10-12-20-35-06
.. nonce: gQM-O7
.. section: Library

Fix quadratic behaviour in the enum module: Creation of enum classes with a
lot of entries was quadratic.

..

.. bpo: 45249
.. date: 2021-10-10-16-14-33
.. nonce: xqLliz
.. section: Library

Fix the behaviour of :func:`traceback.print_exc` when displaying the caret
when the ``end_offset`` in the exception is set to 0. Patch by Pablo Galindo

..

.. bpo: 45416
.. date: 2021-10-10-09-42-34
.. nonce: n35O0_
.. section: Library

Fix use of :class:`asyncio.Condition` with explicit :class:`asyncio.Lock`
objects, which was a regression due to removal of explicit loop arguments.
Patch by Joongi Kim.

..

.. bpo: 20028
.. date: 2021-10-10-00-25-36
.. nonce: bPx4Z8
.. section: Library

Empty escapechar/quotechar is not allowed when initializing
:class:`csv.Dialect`. Patch by Vajrasky Kok and Dong-hee Na.

..

.. bpo: 44904
.. date: 2021-10-09-18-42-27
.. nonce: RlW5h8
.. section: Library

Fix bug in the :mod:`doctest` module that caused it to fail if a docstring
included an example with a ``classmethod`` ``property``. Patch by Alex
Waygood.

..

.. bpo: 45406
.. date: 2021-10-08-19-24-48
.. nonce: Qh_Mz4
.. section: Library

Make :func:`inspect.getmodule` catch ``FileNotFoundError`` raised by
:'func:`inspect.getabsfile`, and return ``None`` to indicate that the module
could not be determined.

..

.. bpo: 45411
.. date: 2021-10-08-11-29-29
.. nonce: 4jR--U
.. section: Library

Add extensions for files containing subtitles - .srt & .vtt - to the
mimetypes.py module.

..

.. bpo: 10716
.. date: 2021-10-08-04-11-55
.. nonce: QSRVK2
.. section: Library

Migrated pydoc to HTML5 (without changing the look of it). Side effect is to
update xmlrpc's ``ServerHTMLDoc`` which now uses the CSS too. cgitb now
relies less on pydoc (as it can't use the CSS file).

..

.. bpo: 27580
.. date: 2021-10-07-21-11-48
.. nonce: tGcBTH
.. section: Library

Add support of null characters in :mod:`csv`.

..

.. bpo: 45262
.. date: 2021-10-07-14-04-10
.. nonce: HqF71Z
.. section: Library

Prevent use-after-free in asyncio. Make sure the cached running loop holder
gets cleared on dealloc to prevent use-after-free in get_running_loop

..

.. bpo: 45386
.. date: 2021-10-07-00-05-05
.. nonce: q9ORpA
.. section: Library

Make :mod:`xmlrpc.client` more robust to C runtimes where the underlying C
``strftime`` function results in a ``ValueError`` when testing for year
formatting options.

..

.. bpo: 20028
.. date: 2021-10-03-21-14-37
.. nonce: zBA4RK
.. section: Library

Improve error message of :class:`csv.Dialect` when initializing. Patch by
Vajrasky Kok and Dong-hee Na.

..

.. bpo: 45343
.. date: 2021-10-01-23-07-02
.. nonce: ixmctD
.. section: Library

Update bundled pip to 21.2.4 and setuptools to 58.1.0

..

.. bpo: 45328
.. date: 2021-09-30-08-22-44
.. nonce: 8Z-Q0B
.. section: Library

Fixed :class:`http.client.HTTPConnection` to work properly in OSs that don't
support the ``TCP_NODELAY`` socket option.

..

.. bpo: 45243
.. date: 2021-09-20-01-25-09
.. nonce: 0pJf0U
.. section: Library

Add :meth:`~sqlite3.Connection.setlimit` and
:meth:`~sqlite3.Connection.getlimit` to :class:`sqlite3.Connection` for
setting and getting SQLite limits by connection basis. Patch by Erlend E.
Aasland.

..

.. bpo: 45320
.. date: 2021-09-15-10-21-10
.. nonce: 4qaf5x
.. section: Library

Removed from the :mod:`inspect` module:

* the ``getargspec`` function, deprecated since Python 3.0;
    use :func:`inspect.signature` or :func:`inspect.getfullargspec` instead.

* the ``formatargspec`` function, deprecated since Python 3.5;
  use the :func:`inspect.signature` function and :class:`Signature` object
  directly.

* the undocumented ``Signature.from_callable`` and ``Signature.from_function``
  functions, deprecated since Python 3.5; use the
  :meth:`Signature.from_callable() <inspect.Signature.from_callable>` method
  instead.

Patch by Hugo van Kemenade.

..

.. bpo: 45192
.. date: 2021-09-14-15-52-47
.. nonce: DjA-BI
.. section: Library

Fix the ``tempfile._infer_return_type`` function so that the ``dir``
argument of the :mod:`tempfile` functions accepts an object implementing the
``os.PathLike`` protocol.

Patch by Kyungmin Lee.

..

.. bpo: 45160
.. date: 2021-09-11-14-47-05
.. nonce: VzMXbW
.. section: Library

When tracing a tkinter variable used by a ttk OptionMenu, callbacks are no
longer made twice.

..

.. bpo: 25625
.. date: 2021-09-10-12-53-28
.. nonce: SzcBCw
.. section: Library

Added non parallel-safe :func:`~contextlib.chdir` context manager to change
the current working directory and then restore it on exit. Simple wrapper
around :func:`~os.chdir`.

..

.. bpo: 24139
.. date: 2021-08-30-23-10-48
.. nonce: e38czf
.. section: Library

Add support for SQLite extended result codes in :exc:`sqlite3.Error`. Patch
by Erlend E. Aasland.

..

.. bpo: 24444
.. date: 2021-08-30-00-19-23
.. nonce: Ki4bgz
.. section: Library

Fixed an error raised in :mod:`argparse` help display when help for an
option is set to 1+ blank spaces or when *choices* arg is an empty
container.

..

.. bpo: 44547
.. date: 2021-08-20-10-52-40
.. nonce: eu0iJq
.. section: Library

Implement ``Fraction.__int__``, so that a :class:`fractions.Fraction`
instance ``f`` passes an ``isinstance(f, typing.SupportsInt)`` check.

..

.. bpo: 40321
.. date: 2021-07-22-21-25-56
.. nonce: gBlFmw
.. section: Library

Adds support for HTTP 308 redirects to :mod:`urllib`. See :rfc:`7538` for
details. Patch by Jochem Schulenklopper.

..

.. bpo: 41374
.. date: 2020-07-27-19-21-05
.. nonce: cd-kFL
.. section: Library

Ensure that ``socket.TCP_*`` constants are exposed on Cygwin 3.1.6 and
greater.

..

.. bpo: 35970
.. date: 2019-02-11-19-06-10
.. nonce: ZRvh51
.. section: Library

Add help flag to the base64 module's command line interface. Patch
contributed by Robert Kuska.

..

.. bpo: 45726
.. date: 2021-11-05-12-15-24
.. nonce: GwRr7e
.. section: Documentation

Improve documentation for :func:`functools.singledispatch` and
:class:`functools.singledispatchmethod`.

..

.. bpo: 45680
.. date: 2021-11-03-14-51-03
.. nonce: 9_NTFU
.. section: Documentation

Amend the docs on ``GenericAlias`` objects to clarify that non-container
classes can also implement ``__class_getitem__``. Patch contributed by Alex
Waygood.

..

.. bpo: 45618
.. date: 2021-10-31-20-35-06
.. nonce: RTcNXF
.. section: Documentation

Update Sphinx version used to build the documentation to 4.2.0. Patch by
Maciej Olko.

..

.. bpo: 45655
.. date: 2021-10-28-19-22-55
.. nonce: aPYGaS
.. section: Documentation

Add a new "relevant PEPs" section to the top of the documentation for the
``typing`` module. Patch by Alex Waygood.

..

.. bpo: 45604
.. date: 2021-10-26-10-00-45
.. nonce: Dm-YhV
.. section: Documentation

Add ``level`` argument to ``multiprocessing.log_to_stderr`` function docs.

..

.. bpo: 45516
.. date: 2021-10-22-21-57-42
.. nonce: 7_RMEX
.. section: Documentation

Add protocol description to the :class:`importlib.abc.TraversableResources`
documentation.

..

.. bpo: 45464
.. date: 2021-10-20-16-26-53
.. nonce: mOISBs
.. section: Documentation

Mention in the documentation of :ref:`Built-in Exceptions
<bltin-exceptions>` that inheriting from multiple exception types in a
single subclass is not recommended due to possible memory layout
incompatibility.

..

.. bpo: 45449
.. date: 2021-10-19-01-41-40
.. nonce: fjHZJc
.. section: Documentation

Add note about :pep:`585` in :mod:`collections.abc`.

..

.. bpo: 45516
.. date: 2021-10-18-20-12-18
.. nonce: EJh4K8
.. section: Documentation

Add protocol description to the :class:`importlib.abc.Traversable`
documentation.

..

.. bpo: 20692
.. date: 2021-10-13-00-42-54
.. nonce: K5rGtP
.. section: Documentation

Add Programming FAQ entry explaining that int literal attribute access
requires either a space after or parentheses around the literal.

..

.. bpo: 45678
.. date: 2021-11-04-20-03-32
.. nonce: 1xNMjN
.. section: Tests

Add tests for scenarios in which :class:`functools.singledispatchmethod` is
stacked on top of a method that has already been wrapped by two other
decorators. Patch by Alex Waygood.

..

.. bpo: 45578
.. date: 2021-10-30-19-00-25
.. nonce: bvu6X2
.. section: Tests

Add tests for :func:`dis.distb`

..

.. bpo: 45678
.. date: 2021-10-30-13-12-20
.. nonce: bKrYeS
.. section: Tests

Add tests to ensure that ``functools.singledispatchmethod`` correctly wraps
the attributes of the target function.

..

.. bpo: 45668
.. date: 2021-10-29-17-18-56
.. nonce: MfAw4i
.. section: Tests

PGO tests now pass when Python is built without test extension modules.

..

.. bpo: 45577
.. date: 2021-10-22-19-44-13
.. nonce: dSaNvK
.. section: Tests

Add subtests for all ``pickle`` protocols in ``test_zoneinfo``.

..

.. bpo: 45566
.. date: 2021-10-22-12-05-21
.. nonce: 2gQ3ZB
.. section: Tests

Fix ``test_frozen_pickle`` in ``test_dataclasses`` to check all ``pickle``
versions.

..

.. bpo: 43592
.. date: 2021-10-21-17-22-26
.. nonce: kHRsra
.. section: Tests

:mod:`test.libregrtest` now raises the soft resource limit for the maximum
number of file descriptors when the default is too low for our test suite as
was often the case on macOS.

..

.. bpo: 39679
.. date: 2021-10-18-16-18-41
.. nonce: F18qcE
.. section: Tests

Add more test cases for `@functools.singledispatchmethod` when combined with
`@classmethod` or `@staticmethod`.

..

.. bpo: 45410
.. date: 2021-10-08-14-03-20
.. nonce: Ex9xe2
.. section: Tests

When libregrtest spawns a worker process, stderr is now written into stdout
to keep messages order. Use a single pipe for stdout and stderr, rather than
two pipes. Previously, messages were out of order which made analysis of
buildbot logs harder Patch by Victor Stinner.

..

.. bpo: 45402
.. date: 2021-10-07-13-43-01
.. nonce: jlQvep
.. section: Tests

Fix test_tools.test_sundry() when Python is built out of tree: fix how the
freeze_modules.py tool locates the _freeze_module program. Patch by Victor
Stinner.

..

.. bpo: 45403
.. date: 2021-10-07-13-27-12
.. nonce: 7QiDvw
.. section: Tests

Fix test_sys.test_stdlib_dir() when Python is built outside the source tree:
compare normalized paths. Patch by Victor Stinner.

..

.. bpo: 45400
.. date: 2021-10-07-13-11-45
.. nonce: h3iT7V
.. section: Tests

Fix test_name_error_suggestions_do_not_trigger_for_too_many_locals() of
test_exceptions if a directory name contains "a1" (like "Python-3.11.0a1"):
use a stricter regular expression. Patch by Victor Stinner.

..

.. bpo: 10572
.. date: 2021-01-07-01-25-38
.. nonce: gEEZ9z
.. section: Tests

Rename :mod:`sqlite3` tests from ``test_sqlite`` to ``test_sqlite3``, and
relocate them to ``Lib/test/test_sqlite3``. Patch by Erlend E. Aasland.

..

.. bpo: 43158
.. date: 2021-11-01-12-51-46
.. nonce: fghS6w
.. section: Build

``setup.py`` now uses values from configure script to build the ``_uuid``
extension module. Configure now detects util-linux's ``libuuid``, too.

..

.. bpo: 45666
.. date: 2021-10-29-12-54-53
.. nonce: w2G63u
.. section: Build

Fix warning of ``swprintf`` and ``%s`` usage in ``_testembed.c``

..

.. bpo: 45548
.. date: 2021-10-28-14-47-22
.. nonce: mdCBxB
.. section: Build

``Modules/Setup`` and ``Modules/makesetup`` have been improved. The
``Setup`` file now contains working rules for all extensions. Outdated
comments have been removed. Rules defined by ``makesetup`` track
dependencies correctly.

..

.. bpo: 45548
.. date: 2021-10-24-21-49-49
.. nonce: UWx0UC
.. section: Build

The :mod:`math` and :mod:`cmath` implementation now require a C99 compatible
``libm`` and no longer ship with workarounds for missing acosh, asinh,
atanh, expm1, and log1p functions.

..

.. bpo: 45595
.. date: 2021-10-24-11-02-43
.. nonce: WI_5YU
.. section: Build

``setup.py`` and ``makesetup`` now track build dependencies on all Python
header files and module specific header files.

..

.. bpo: 45571
.. date: 2021-10-22-15-28-29
.. nonce: yY8NsJ
.. section: Build

``Modules/Setup`` now use ``PY_CFLAGS_NODIST`` instead of ``PY_CFLAGS`` to
compile shared modules.

..

.. bpo: 45570
.. date: 2021-10-22-14-45-40
.. nonce: 61gM2A
.. section: Build

:mod:`pyexpat` and :mod:`_elementtree` no longer define obsolete macros
``HAVE_EXPAT_CONFIG_H`` and ``USE_PYEXPAT_CAPI``. ``XML_POOR_ENTROPY`` is
now defined in ``expat_config.h``.

..

.. bpo: 43974
.. date: 2021-10-22-14-00-44
.. nonce: HHZtbx
.. section: Build

``setup.py`` no longer defines ``Py_BUILD_CORE_MODULE``. Instead every
module, that uses the internal API, defines the macro.

..

.. bpo: 45548
.. date: 2021-10-20-17-02-56
.. nonce: BoggEf
.. section: Build

Fill in missing entries in Modules/Setup.

..

.. bpo: 45532
.. date: 2021-10-20-16-07-39
.. nonce: kyhvis
.. section: Build

Update :data:`sys.version` to use ``main`` as fallback information. Patch by
Jeong YunWon.

..

.. bpo: 45536
.. date: 2021-10-20-12-42-39
.. nonce: oQNYHB
.. section: Build

The ``configure`` script now checks whether OpenSSL headers and libraries
provide required APIs. Most common APIs are verified. The check detects
outdated or missing OpenSSL. Failures do not stop configure.

..

.. bpo: 45221
.. date: 2021-10-18-10-25-56
.. nonce: rnulhf
.. section: Build

Fixed regression in handling of ``LDFLAGS`` and ``CPPFLAGS`` options where
:meth:`argparse.parse_known_args` could interpret an option as one of the
built-in command line argument, for example ``-h`` for help.

..

.. bpo: 45440
.. date: 2021-10-12-02-13-08
.. nonce: -zYgDb
.. section: Build

Building Python now requires a C99 ``<math.h>`` header file providing the
following functions: ``copysign()``, ``hypot()``, ``isfinite()``,
``isinf()``, ``isnan()``, ``round()``. Patch by Victor Stinner.

..

.. bpo: 45405
.. date: 2021-10-11-16-27-38
.. nonce: iSfdW5
.. section: Build

Prevent ``internal configure error`` when running ``configure`` with recent
versions of non-Apple clang.  Patch by David Bohman.

..

.. bpo: 45433
.. date: 2021-10-11-16-08-37
.. nonce: pVDkMV
.. section: Build

Avoid linking libpython with libcrypt.

..

.. bpo: 43652
.. date: 2021-11-04-00-41-50
.. nonce: RnqV7I
.. section: Windows

Update Tcl/Tk to 8.6.11, actually this time. The previous update incorrectly
included 8.6.10.

..

.. bpo: 45337
.. date: 2021-09-30-23-17-27
.. nonce: qg7U_h
.. section: Windows

venv now warns when the created environment may need to be accessed at a
different path, due to redirections, links or junctions. It also now
correctly installs or upgrades components when the alternate path is
required.

..

.. bpo: 43851
.. date: 2021-04-15-01-23-10
.. nonce: qgU0gy
.. section: Windows

Build SQLite ``SQLITE_OMIT_AUTOINIT`` on Windows. Patch by Erlend E.
Aasland.

..

.. bpo: 44828
.. date: 2021-10-25-02-02-21
.. nonce: XBdXlJ
.. section: macOS

Avoid tkinter file dialog failure on macOS 12 Monterey when using the Tk
8.6.11 provided by python.org macOS installers. Patch by Marc Culler of the
Tk project.

..

.. bpo: 45495
.. date: 2021-10-16-17-20-32
.. nonce: ST8RFt
.. section: IDLE

Add context keywords 'case' and 'match' to completions list.

..

.. bpo: 29103
.. date: 2021-10-20-18-41-17
.. nonce: CMRLyq
.. section: C API

:c:func:`PyType_FromSpec* <PyType_FromModuleAndSpec>` now copies the class
name from the spec to a buffer owned by the class, so the original can be
safely deallocated. Patch by Petr Viktorin.

..

.. bpo: 45522
.. date: 2021-10-19-13-07-46
.. nonce: kGAwmZ
.. section: C API

The internal freelists for frame, float, list, dict, async generators, and
context objects can now be disabled.

..

.. bpo: 35134
.. date: 2021-10-19-00-20-40
.. nonce: Z0Zk_m
.. section: C API

Exclude :c:func:`PyWeakref_GET_OBJECT` from the limited C API. It never
worked since the :c:type:`PyWeakReference` structure is opaque in the
limited C API.

..

.. bpo: 35081
.. date: 2021-10-15-09-29-59
.. nonce: 2teFD3
.. section: C API

Move the ``interpreteridobject.h`` header file from ``Include/`` to
``Include/internal/``. It only provides private functions. Patch by Victor
Stinner.

..

.. bpo: 35134
.. date: 2021-10-15-00-11-51
.. nonce: eX4zqy
.. section: C API

The non-limited API files ``cellobject.h``, ``classobject.h``,
``context.h``, ``funcobject.h``, ``genobject.h`` and ``longintrepr.h`` have
been moved to the ``Include/cpython`` directory. Moreover, the ``eval.h``
header file was removed. These files must not be included directly, as they
are already included in ``Python.h``: :ref:`Include Files <api-includes>`.
If they have been included directly, consider including ``Python.h``
instead. Patch by Victor Stinner.

..

.. bpo: 45474
.. date: 2021-10-14-22-16-56
.. nonce: 1OkJQh
.. section: C API

The following items are no longer available when ``Py_LIMITED_API`` is
defined:

* :c:func:`PyMarshal_WriteLongToFile`
* :c:func:`PyMarshal_WriteObjectToFile`
* :c:func:`PyMarshal_ReadObjectFromString`
* :c:func:`PyMarshal_WriteObjectToString`
* the ``Py_MARSHAL_VERSION`` macro

These are not part of the :ref:`limited API <stable-abi-list>`.

Patch by Victor Stinner.

..

.. bpo: 45434
.. date: 2021-10-13-14-42-46
.. nonce: INNEEt
.. section: C API

Remove the ``pystrhex.h`` header file. It only contains private functions. C
extensions should only include the main ``<Python.h>`` header file. Patch by
Victor Stinner.

..

.. bpo: 45440
.. date: 2021-10-12-02-13-41
.. nonce: Gf94rE
.. section: C API

Remove the ``Py_FORCE_DOUBLE()`` macro. It was used by the
``Py_IS_INFINITY()`` macro. Patch by Victor Stinner.

..

.. bpo: 45434
.. date: 2021-10-11-23-03-49
.. nonce: tsS8I_
.. section: C API

``<Python.h>`` no longer includes the header files ``<stdlib.h>``,
``<stdio.h>``, ``<errno.h>`` and ``<string.h>`` when the ``Py_LIMITED_API``
macro is set to ``0x030b0000`` (Python 3.11) or higher. C extensions should
explicitly include the header files after ``#include <Python.h>``. Patch by
Victor Stinner.

..

.. bpo: 41123
.. date: 2021-10-11-22-58-33
.. nonce: myrlIp
.. section: C API

Remove ``Py_UNICODE_COPY()`` and ``Py_UNICODE_FILL()`` macros, deprecated
since Python 3.3. Use ``PyUnicode_CopyCharacters()`` or ``memcpy()``
(``wchar_t*`` string), and ``PyUnicode_Fill()`` functions instead. Patch by
Victor Stinner.

..

.. bpo: 45412
.. date: 2021-10-08-15-54-07
.. nonce: KHyJCT
.. section: C API

Remove the following math macros using the ``errno`` variable:

* ``Py_ADJUST_ERANGE1()``
* ``Py_ADJUST_ERANGE2()``
* ``Py_OVERFLOWED()``
* ``Py_SET_ERANGE_IF_OVERFLOW()``
* ``Py_SET_ERRNO_ON_MATH_ERROR()``

Patch by Victor Stinner.

..

.. bpo: 45395
.. date: 2021-10-06-15-54-40
.. nonce: yVhdAl
.. section: C API

Custom frozen modules (the array set to ``PyImport_FrozenModules``) are now
treated as additions, rather than replacing all the default frozen modules.
Frozen stdlib modules can still be disabled by setting the "code" field of
the custom array entry to NULL.

..

.. bpo: 43760
.. date: 2021-09-24-11-12-21
.. nonce: Bfxd1-
.. section: C API

Add new :c:func:`PyThreadState_EnterTracing`, and
:c:func:`PyThreadState_LeaveTracing` functions to the limited C API to
suspend and resume tracing and profiling. Patch by Victor Stinner.

..

.. bpo: 44220
.. date: 2021-05-24-22-12-40
.. nonce: H9CUGl
.. section: C API

:c:var:`PyStructSequence_UnnamedField` is added to the Stable ABI.