Sync pre-release CPython 3.15 branch from GitHub (2026-07-25)

Summary:
Imported python/cpython `3.15.0b4+dev` from upstream rev [`1667a6c`](https://www.github.com/python/cpython/commit/1667a6c2acb022ecca37d3dc68b3d67ef186215e) (committed 2026-07-25 15:17:11+00:00).

# Commit Info

- Base: (`3.15.0b4+dev`) - [`b4d0b26`](https://www.github.com/python/cpython/commit/b4d0b2621a97f8433e25bb88cbd9c815fff7abe0) (commit date: 2026-07-25 03:36:48+00:00)
- Imported: (`3.15.0b4+dev`) - [`1667a6c`](https://www.github.com/python/cpython/commit/1667a6c2acb022ecca37d3dc68b3d67ef186215e) (commit date: 2026-07-25 15:17:11+00:00)

# Noteworthy file changes

- Low-signal files (3 added) (NEWS.d, docs, .github)

Complete list of added/removed files: https://www.internalfb.com/intern/everpaste/?color=0&handle=GIaiuCQuFzf_u90DAIt02g83aewabr0LAAAz

Differential Revision: D113686228

fbshipit-source-id: 567d957526eb988090a7eb7f80fe18abb7341426

Author: generatedunixname1734921407115435

.gitignore

@@ -124,10 +124,14 @@ PCbuild/*-pgo
 PCbuild/*.VC.db
 PCbuild/*.VC.opendb
 PCbuild/amd64/
+PCbuild/amd64t/
 PCbuild/arm32/
+PCbuild/arm32t/
 PCbuild/arm64/
+PCbuild/arm64t/
 PCbuild/obj/
 PCbuild/win32/
+PCbuild/win32t/
 Tools/unicode/data/
 /autom4te.cache
 /build/

Doc/library/asyncio-eventloop.rst

@@ -1884,6 +1884,12 @@ Do not instantiate the :class:`Server` class directly.
       Wait until the :meth:`close` method completes and all active
       connections have finished.
 
+      .. versionchanged:: 3.12
+         ``wait_closed()`` now waits until the server is closed and
+         all active connections have finished.  Previously, it returned
+         immediately if the server was already closed, even if
+         connections were still active.
+
    .. attribute:: sockets
 
       List of socket-like objects, ``asyncio.trsock.TransportSocket``, which

Doc/license.rst

@@ -1216,3 +1216,52 @@ license::
   LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
   DAMAGE.
+
+
+Unicode Character Database
+--------------------------
+
+An extract of the `Unicode Character Database <https://www.unicode.org/ucd/>`__,
+converted to an internal format, is used by the :mod:`unicodedata` module and
+for the Unicode support of the :class:`str` type. The original Unicode data
+files are distributed under the `Unicode License <https://www.unicode.org/license.txt>`__::
+
+  UNICODE LICENSE V3
+
+  COPYRIGHT AND PERMISSION NOTICE
+
+  Copyright © 1991-2026 Unicode, Inc.
+
+  NOTICE TO USER: Carefully read the following legal agreement. BY
+  DOWNLOADING, INSTALLING, COPYING OR OTHERWISE USING DATA FILES, AND/OR
+  SOFTWARE, YOU UNEQUIVOCALLY ACCEPT, AND AGREE TO BE BOUND BY, ALL OF THE
+  TERMS AND CONDITIONS OF THIS AGREEMENT. IF YOU DO NOT AGREE, DO NOT
+  DOWNLOAD, INSTALL, COPY, DISTRIBUTE OR USE THE DATA FILES OR SOFTWARE.
+
+  Permission is hereby granted, free of charge, to any person obtaining a
+  copy of data files and any associated documentation (the "Data Files") or
+  software and any associated documentation (the "Software") to deal in the
+  Data Files or Software without restriction, including without limitation
+  the rights to use, copy, modify, merge, publish, distribute, and/or sell
+  copies of the Data Files or Software, and to permit persons to whom the
+  Data Files or Software are furnished to do so, provided that either (a)
+  this copyright and permission notice appear with all copies of the Data
+  Files or Software, or (b) this copyright and permission notice appear in
+  associated Documentation.
+
+  THE DATA FILES AND SOFTWARE ARE PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
+  KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF
+  THIRD PARTY RIGHTS.
+
+  IN NO EVENT SHALL THE COPYRIGHT HOLDER OR HOLDERS INCLUDED IN THIS NOTICE
+  BE LIABLE FOR ANY CLAIM, OR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES,
+  OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+  WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
+  ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THE DATA
+  FILES OR SOFTWARE.
+
+  Except as contained in this notice, the name of a copyright holder shall
+  not be used in advertising or otherwise to promote the sale, use or other
+  dealings in these Data Files or Software without prior written
+  authorization of the copyright holder.

Lib/asyncio/streams.py

@@ -216,6 +216,9 @@ def _stream_reader(self):
     def _replace_transport(self, transport):
         self._transport = transport
         self._over_ssl = transport.get_extra_info('sslcontext') is not None
+        reader = self._stream_reader
+        if reader is not None:
+            reader._replace_transport(transport)
 
     def connection_made(self, transport):
         if self._reject_connection:
@@ -475,6 +478,10 @@ def set_transport(self, transport):
         assert self._transport is None, 'Transport already set'
         self._transport = transport
 
+    def _replace_transport(self, transport):
+        assert self._transport is not None, 'Transport not set'
+        self._transport = transport
+
     def _maybe_resume_transport(self):
         if self._paused and len(self._buffer) <= self._limit:
             self._paused = False

Lib/asyncio/unix_events.py

@@ -639,7 +639,8 @@ def __init__(self, loop, pipe, protocol, waiter=None, extra=None):
         self._conn_lost = 0
         self._closing = False  # Set when close() or write_eof() called.
 
-        mode = os.fstat(self._fileno).st_mode
+        pipe_stat = os.fstat(self._fileno)
+        mode = pipe_stat.st_mode
         is_char = stat.S_ISCHR(mode)
         is_fifo = stat.S_ISFIFO(mode)
         is_socket = stat.S_ISSOCK(mode)
@@ -656,7 +657,19 @@ def __init__(self, loop, pipe, protocol, waiter=None, extra=None):
         # On AIX, the reader trick (to be notified when the read end of the
         # socket is closed) only works for sockets. On other platforms it
         # works for pipes and sockets. (Exception: OS X 10.4?  Issue #19294.)
-        if is_socket or (is_fifo and not sys.platform.startswith("aix")):
+        # On macOS, the trick misfires for named FIFOs (but not for pipes
+        # created with os.pipe(), which have st_nlink == 0): the write end
+        # polls as readable whenever unread data sits in the FIFO, and no
+        # event is delivered when the read end is closed, so it can only
+        # ever report a false disconnection (gh-145030). The same xnu
+        # behaviour applies on iOS/tvOS/watchOS (sys.platform is not
+        # "darwin" there).
+        is_named_fifo_on_apple = (
+            sys.platform in {"darwin", "ios", "tvos", "watchos"}
+            and is_fifo and pipe_stat.st_nlink > 0)
+        if is_socket or (is_fifo
+                         and not sys.platform.startswith("aix")
+                         and not is_named_fifo_on_apple):
             # only start reading when connection_made() has been called
             self._loop.call_soon(self._loop._add_reader,
                                  self._fileno, self._read_ready)

Lib/test/test_asyncio/test_events.py

@@ -1725,6 +1725,48 @@ def reader(data):
         self.loop.run_until_complete(proto.done)
         self.assertEqual('CLOSED', proto.state)
 
+    @unittest.skipUnless(sys.platform != 'win32',
+                         "Don't support pipes for Windows")
+    @unittest.skipUnless(hasattr(os, 'mkfifo'), 'requires os.mkfifo()')
+    def test_write_named_fifo_unread_data(self):
+        # gh-145030: on macOS, the write end of a named FIFO polls as
+        # readable while unread data sits in the FIFO, which made the
+        # transport misinterpret the event as the reader hanging up
+        # and close itself.
+        path = os_helper.TESTFN
+        os.mkfifo(path)
+        self.assertNotEqual(os.stat(path).st_nlink, 0)
+        self.addCleanup(os_helper.unlink, path)
+        rfd = os.open(path, os.O_RDONLY | os.O_NONBLOCK)
+        self.addCleanup(os.close, rfd)
+        wfd = os.open(path, os.O_WRONLY | os.O_NONBLOCK)
+        pipeobj = io.open(wfd, 'wb', 1024)
+
+        proto = MyWritePipeProto(loop=self.loop)
+        connect = self.loop.connect_write_pipe(lambda: proto, pipeobj)
+        transport, p = self.loop.run_until_complete(connect)
+        self.assertIs(p, proto)
+        self.assertEqual('CONNECTED', proto.state)
+
+        transport.write(b'1')
+        # Iterate the event loop while the data stays unread in the FIFO;
+        # the transport must not detect a false disconnection.
+        for _ in range(10):
+            test_utils.run_briefly(self.loop)
+        self.assertEqual('CONNECTED', proto.state)
+        self.assertFalse(transport.is_closing())
+        self.assertEqual(b'1', os.read(rfd, 1024))
+
+        transport.write(b'2345')
+        for _ in range(10):
+            test_utils.run_briefly(self.loop)
+        self.assertEqual('CONNECTED', proto.state)
+        self.assertEqual(b'2345', os.read(rfd, 1024))
+
+        transport.close()
+        self.loop.run_until_complete(proto.done)
+        self.assertEqual('CLOSED', proto.state)
+
     @unittest.skipUnless(sys.platform != 'win32',
                          "Don't support pipes for Windows")
     def test_write_pipe_disconnect_on_close(self):

Lib/test/test_asyncio/test_streams.py

@@ -861,6 +861,34 @@ async def run_test():
         self.loop.run_until_complete(run_test())
         self.assertEqual(messages, [])
 
+    def test_streamwriter_start_tls_updates_reader_transport(self):
+        reader = asyncio.StreamReader(loop=self.loop)
+        protocol = asyncio.StreamReaderProtocol(reader, loop=self.loop)
+        old_transport = mock.Mock()
+        old_transport.get_extra_info.return_value = None
+        old_transport.is_closing.return_value = False
+        protocol.connection_made(old_transport)
+
+        writer = asyncio.StreamWriter(old_transport, protocol, reader, self.loop)
+
+        ssl_context = mock.sentinel.ssl_context
+        new_transport = mock.Mock()
+        new_transport.get_extra_info.return_value = ssl_context
+        self.loop.start_tls = mock.AsyncMock(return_value=new_transport)
+
+        self.loop.run_until_complete(writer.start_tls(ssl_context))
+
+        self.loop.start_tls.assert_awaited_once_with(
+            old_transport, protocol, ssl_context,
+            server_side=False, server_hostname=None,
+            ssl_handshake_timeout=None,
+            ssl_shutdown_timeout=None,
+        )
+        self.assertIs(writer.transport, new_transport)
+        self.assertIs(protocol._transport, new_transport)
+        self.assertIs(reader._transport, new_transport)
+        self.assertTrue(protocol._over_ssl)
+
     def test_streamreader_constructor_without_loop(self):
         with self.assertRaisesRegex(RuntimeError, 'no current event loop'):
             asyncio.StreamReader()

Misc/NEWS.d/next/Core_and_Builtins/2026-07-24-13-15-31.gh-issue-153809.JFA6GT.rst

@@ -0,0 +1,2 @@
+Fix interpreter crash while deallocating objects of :class:`asyncio.Task` on
+free-threaded builds. Contributed by Sergey Miryanov.

Misc/NEWS.d/next/Library/2026-06-28-00-00-00.gh-issue-152431.Ja3K9m.rst

@@ -0,0 +1,2 @@
+Fix ``asyncio.StreamWriter.start_tls()`` to keep the linked
+``StreamReader`` transport in sync with the upgraded transport.

Misc/NEWS.d/next/Library/2026-07-20-12-40-00.gh-issue-145030.TFJm6k.rst

@@ -0,0 +1,3 @@
+Fix :mod:`asyncio` write pipe transports for named FIFOs on macOS.  Unread
+data sitting in the FIFO made the transport misinterpret a poll event as
+the reader disconnecting, wrongly closing the transport.