Sync pre-release CPython main branch from GitHub (2026-07-13)

Summary:
Imported python/cpython `3.16.0a0` from upstream rev [`1fece44`](https://www.github.com/python/cpython/commit/1fece4457032382947c7c2a5c9e95dc106ca7a7d) (committed 2026-07-13 09:46:24+00:00).

# Commit Info

- Base: (`3.16.0a0`) - [`6c389c4`](https://www.github.com/python/cpython/commit/6c389c446e487bcb9d09e85de30aa42052990f1c) (commit date: 2026-07-10 02:38:58+00:00)
- Imported: (`3.16.0a0`) - [`1fece44`](https://www.github.com/python/cpython/commit/1fece4457032382947c7c2a5c9e95dc106ca7a7d) (commit date: 2026-07-13 09:46:24+00:00)

# Noteworthy file changes

- Native files (6 added):
  ```
  + Modules/expat/fallthrough.h
  + Modules/expat/memory_sanitizer.h
  + Modules/expat/xcsinc.c
  + Parser/lexer/lexer_internal.h
  + Parser/lexer/number.c
  + Parser/lexer/string.c
  ```
- Stdlib files (2 added)
- Test files (2 added)
- Low-signal files (24 added) (NEWS.d, docs, .github)

Complete list of added/removed files: https://www.internalfb.com/intern/everpaste/?color=0&handle=GD0hQSUpb2ftKv5eAF9SsewHillsbr0LAAAz

Reviewed By: QuantumManiac

Differential Revision: D111728640

fbshipit-source-id: 0ad2d621568c0b4ec824666ea84aba0040d11d5d

Author: itamaro

.github/workflows/build.yml

@@ -554,6 +554,7 @@ jobs:
         - Thread
         free-threading:
         - false
+        - true
         sanitizer:
         - TSan
         include:
@@ -565,17 +566,6 @@ jobs:
       sanitizer: ${{ matrix.sanitizer }}
       free-threading: ${{ matrix.free-threading }}
 
-  # XXX: Temporarily allow this job to fail to not block PRs.
-  build-san-free-threading:
-    # ${{ '' } is a hack to nest jobs under the same sidebar category.
-    name: Sanitizers${{ '' }}  # zizmor: ignore[obfuscation]
-    needs: build-context
-    if: needs.build-context.outputs.run-ubuntu == 'true'
-    uses: ./.github/workflows/reusable-san.yml
-    with:
-      sanitizer: TSan
-      free-threading: true
-
   cross-build-linux:
     name: Cross build Linux
     runs-on: ubuntu-26.04
@@ -679,7 +669,6 @@ jobs:
     - test-hypothesis
     - build-asan
     - build-san
-    - build-san-free-threading
     - cross-build-linux
     - cifuzz
     if: always()
@@ -691,7 +680,6 @@ jobs:
         allowed-failures: >-
           build-android,
           build-emscripten,
-          build-san-free-threading,
           build-windows-msi,
           build-ubuntu-ssltests,
           test-hypothesis,

Doc/c-api/float.rst

@@ -233,9 +233,6 @@ most likely :exc:`OverflowError`).
 
    Pack a C double as the IEEE 754 binary64 double precision format.
 
-   .. impl-detail::
-      This function always succeeds in CPython.
-
 
 Unpack functions
 ^^^^^^^^^^^^^^^^
@@ -251,9 +248,6 @@ Return value: The unpacked double.  On error, this is ``-1.0`` and
 :c:func:`PyErr_Occurred` is true (and an exception is set, most likely
 :exc:`OverflowError`).
 
-.. impl-detail::
-    These functions always succeed in CPython.
-
 .. c:function:: double PyFloat_Unpack2(const char *p, int le)
 
    Unpack the IEEE 754 binary16 half-precision format as a C double.

Doc/deprecations/pending-removal-in-3.19.rst

@@ -40,3 +40,11 @@ Pending removal in Python 3.19
     Before Python 3.14, this property was used to implement the corresponding
     ``read()`` and ``readline()`` methods for :class:`~imaplib.IMAP4` but this
     is no longer the case since then.
+
+* :mod:`tkinter`:
+
+  * :func:`tkinter.filedialog.askopenfiles` has been deprecated since Python
+    3.16.  Iterate over the names returned by
+    :func:`~tkinter.filedialog.askopenfilenames` and open them one by one
+    instead.
+    (Contributed by Serhiy Storchaka in :gh:`152638`.)

Doc/library/asyncio-eventloop.rst

@@ -1145,12 +1145,21 @@ convenient.
 
    *sock* must be a non-blocking socket.
 
+   With :class:`SelectorEventLoop`, *address* does not need to be resolved:
+   for :const:`~socket.AF_INET` and :const:`~socket.AF_INET6` sockets,
+   ``sock_connect`` first checks whether *address* is already resolved by
+   calling :func:`socket.inet_pton`, and uses :meth:`loop.getaddrinfo` to
+   resolve it if it is not.
+
+   :class:`ProactorEventLoop`, the default event loop on Windows, does not
+   resolve *address*.  The host must already be a numeric IP address; passing
+   a host name raises :exc:`OSError`.  Resolve the address with
+   :meth:`loop.getaddrinfo` first, or use :meth:`loop.create_connection`,
+   which resolves the address on every platform.
+
    .. versionchanged:: 3.5.2
-      ``address`` no longer needs to be resolved.  ``sock_connect``
-      will try to check if the *address* is already resolved by calling
-      :func:`socket.inet_pton`.  If not,
-      :meth:`loop.getaddrinfo` will be used to resolve the
-      *address*.
+      With :class:`SelectorEventLoop`, ``address`` no longer needs to be
+      resolved.
 
    .. seealso::
 

Doc/library/asyncio-queue.rst

@@ -71,6 +71,8 @@ Queue
       Return an item if one is immediately available, else raise
       :exc:`QueueEmpty`.
 
+      Raises :exc:`QueueShutDown` if the queue has been shut down and is empty.
+
    .. method:: join()
       :async:
 
@@ -96,6 +98,8 @@ Queue
 
       If no free slot is immediately available, raise :exc:`QueueFull`.
 
+      Raises :exc:`QueueShutDown` if the queue has been shut down.
+
    .. method:: qsize()
 
       Return the number of items in the queue.
@@ -188,8 +192,9 @@ Exceptions
 
 .. exception:: QueueShutDown
 
-   Exception raised when :meth:`~Queue.put` or :meth:`~Queue.get` is
-   called on a queue which has been shut down.
+   Exception raised when :meth:`~Queue.put`, :meth:`~Queue.put_nowait`,
+   :meth:`~Queue.get` or :meth:`~Queue.get_nowait` is called
+   on a queue which has been shut down.
 
    .. versionadded:: 3.13
 

Doc/library/asyncio-task.rst

@@ -924,6 +924,9 @@ Waiting primitives
    Unlike :func:`~asyncio.wait_for`, ``wait()`` does not cancel the
    futures when a timeout occurs.
 
+   If ``wait()`` is cancelled, the futures in *aws* are not cancelled
+   and continue to run.
+
    .. versionchanged:: 3.10
       Removed the *loop* parameter.
 
@@ -981,6 +984,10 @@ Waiting primitives
    are done. This is raised by the ``async for`` loop during asynchronous
    iteration or by the coroutines yielded during plain iteration.
 
+   ``as_completed()`` does not cancel the tasks running the supplied
+   awaitables: if a timeout occurs or the iteration is cancelled, the
+   remaining tasks continue to run.
+
    .. versionchanged:: 3.10
       Removed the *loop* parameter.
 

Doc/library/asyncio-tools.rst

@@ -24,7 +24,7 @@ The following commands inspect the process identified by ``PID``:
 
 The commands read the target process state without executing any code in it.
 They are only available on supported platforms and may require permission to
-inspect another process.  See the :ref:`permission-requirements <permission-requirements>` for details.
+inspect another process.  See the :ref:`permission requirements <permission-requirements>` for details.
 
 .. seealso::
 

Doc/library/dialog.rst

@@ -163,15 +163,23 @@ cancelled it is the empty value documented for that function -- an empty
 string, an empty tuple, an empty list or ``None``.
 
 .. function:: askopenfile(mode="r", **options)
-              askopenfiles(mode="r", **options)
 
-   Create an :class:`Open` dialog.
-   :func:`askopenfile` returns the opened file object, or ``None`` if the
-   dialog is cancelled.
-   :func:`askopenfiles` returns a list of the opened file objects, or an empty
-   list if cancelled.
+   Create an :class:`Open` dialog and return the opened file object,
+   or ``None`` if the dialog is cancelled.
+   The file is opened in mode *mode* (read-only ``'r'`` by default).
+
+.. function:: askopenfiles(mode="r", **options)
+
+   Create an :class:`Open` dialog and return a list of the opened file objects,
+   or an empty list if cancelled.
    The files are opened in mode *mode* (read-only ``'r'`` by default).
 
+   .. deprecated-removed:: next 3.19
+      Opening several files at once is error-prone,
+      and the returned list cannot be used in a :keyword:`with` statement.
+      Iterate over the names returned by :func:`askopenfilenames`
+      and open them one by one instead.
+
 .. function:: asksaveasfile(mode="w", **options)
 
    Create a :class:`SaveAs` dialog and return the opened file object, or
@@ -201,19 +209,16 @@ string, an empty tuple, an empty list or ``None``.
 
 .. class:: Open(master=None, **options)
            SaveAs(master=None, **options)
+           Directory(master=None, **options)
 
-   The above two classes provide native dialog windows for saving and loading
-   files.
+   The above three classes provide native dialog windows for loading and saving
+   files and for selecting a directory.
 
 **Convenience classes**
 
 The below classes are used for creating file/directory windows from scratch.
 These do not emulate the native look-and-feel of the platform.
 
-.. class:: Directory(master=None, **options)
-
-   Create a dialog prompting the user to select a directory.
-
 .. note::  The *FileDialog* class should be subclassed for custom event
    handling and behaviour.
 
@@ -353,23 +358,25 @@ the classic (non-themed) Tk widgets.
 
 .. data:: DIALOG_ICON
 
-   The name of the default bitmap (``'questhead'``) displayed by a
-   :class:`Dialog`.
+   The name of a bitmap (``'questhead'``) suitable for use as the *bitmap*
+   of a :class:`Dialog`.
 
 .. class:: Dialog(master=None, cnf={}, **kw)
 
    Display a modal dialog box built from the classic (non-themed) Tk widgets
    and wait for the user to press one of its buttons.
-   The options, given through *cnf* or as keyword arguments, include *title*
-   (the window title), *text* (the message), *bitmap* (an icon,
-   :data:`DIALOG_ICON` by default), *default* (the index of the default button)
-   and *strings* (the sequence of button labels).
+   The options, given through *cnf* or as keyword arguments, are all required:
+   *title* (the window title), *text* (the message), *bitmap* (the name of a
+   bitmap icon, such as :data:`DIALOG_ICON`), *default* (the index of the
+   default button) and *strings* (the sequence of button labels).
    After construction, the :attr:`!num` attribute holds the index of the button
    the user pressed.
 
    .. method:: destroy()
 
-      Destroy the dialog window.
+      Do nothing.
+      The dialog window is destroyed automatically before the constructor
+      returns, so there is nothing left for this method to do.
 
 
 .. seealso::