Sync pre-release CPython 3.15 branch from GitHub (2026-06-13)

Summary:
Imported python/cpython `3.15.0b2+dev` from upstream rev [`75289a9`](https://www.github.com/python/cpython/commit/75289a92dfb460acde427b9f399881a108427b6c) (committed 2026-06-13 23:40:19+00:00).

# Commit Info

- Base: (`3.15.0b2+dev`) - [`a2e5516`](https://www.github.com/python/cpython/commit/a2e551610f6248cfd130172e1cf9f5ee811758b9) (commit date: 2026-06-12 01:47:01+00:00)
- Imported: (`3.15.0b2+dev`) - [`75289a9`](https://www.github.com/python/cpython/commit/75289a92dfb460acde427b9f399881a108427b6c) (commit date: 2026-06-13 23:40:19+00:00)

# Noteworthy file changes

- Low-signal files (4 added) (NEWS.d, docs, .github)

Complete list of added/removed files: https://www.internalfb.com/intern/everpaste/?color=0&handle=GAlRSyBZB6EslScJAPwquOqAdDAJbr0LAAAz

Differential Revision: D108538177

fbshipit-source-id: 4ff7f84c9ad92788b8a057a72621ea49385b97b6

Author: generatedunixname1734921407115435

.github/workflows/reusable-san.yml

@@ -82,13 +82,10 @@ jobs:
       run: make -j4
     - name: Display build info
       run: make pythoninfo
-    # test_capi is skipped under UBSan because
-    # they raise signals that UBSan with halt_on_error=1 intercepts.
     - name: Tests
       run: >-
         ./python -m test
         ${{ inputs.sanitizer == 'TSan' && '--tsan' || '' }}
-        ${{ inputs.sanitizer == 'UBSan' && '-x test_capi' || '' }}
         -j4 -W
     - name: Parallel tests
       if: >-

Doc/library/curses.ascii.rst

@@ -130,7 +130,7 @@ C library:
 
 .. function:: isgraph(c)
 
-   Checks for ASCII any printable character except space.
+   Checks for any ASCII printable character except space.
 
 
 .. function:: islower(c)
@@ -145,7 +145,7 @@ C library:
 
 .. function:: ispunct(c)
 
-   Checks for any printable ASCII character which is not a space or an alphanumeric
+   Checks for any ASCII printable character which is not a space or an alphanumeric
    character.
 
 

Doc/library/enum.rst

@@ -629,7 +629,7 @@ Data types
          >>> white in purple
          False
 
-   .. method:: __iter__(self):
+   .. method:: __iter__(self)
 
       Returns all contained non-alias members::
 
@@ -640,7 +640,7 @@ Data types
 
       .. versionadded:: 3.11
 
-   .. method:: __len__(self):
+   .. method:: __len__(self)
 
       Returns number of members in flag::
 
@@ -651,7 +651,7 @@ Data types
 
       .. versionadded:: 3.11
 
-   .. method:: __bool__(self):
+   .. method:: __bool__(self)
 
       Returns *True* if any members in flag, *False* otherwise::
 
@@ -688,7 +688,7 @@ Data types
          >>> purple ^ Color.GREEN
          <Color.RED|GREEN|BLUE: 7>
 
-   .. method:: __invert__(self):
+   .. method:: __invert__(self)
 
       Returns all the flags in *type(self)* that are not in *self*::
 

Doc/library/functions.rst

@@ -485,7 +485,7 @@ are always available.  They are listed here in alphabetical order.
    :noindex:
 
    Create a new dictionary.  The :class:`dict` object is the dictionary class.
-   See :class:`dict` and :ref:`typesmapping` for documentation about this class.
+   See also :ref:`typesmapping` for documentation about this class.
 
    For other containers see the built-in :class:`frozendict`, :class:`list`,
    :class:`set`, and :class:`tuple` classes, as well as the :mod:`collections` module.
@@ -873,7 +873,7 @@ are always available.  They are listed here in alphabetical order.
    :noindex:
 
    Create a new frozen dictionary.  The :class:`frozendict` object is a built-in class.
-   See :class:`frozendict` and :ref:`typesmapping` for documentation about this class.
+   See also :ref:`typesmapping` for documentation about this class.
 
    For other containers see the built-in :class:`dict`, :class:`list`, :class:`set`,
    and :class:`tuple` classes, as well as the :mod:`collections` module.
@@ -886,7 +886,7 @@ are always available.  They are listed here in alphabetical order.
    :noindex:
 
    Return a new :class:`frozenset` object, optionally with elements taken from
-   *iterable*.  ``frozenset`` is a built-in class.  See :class:`frozenset` and
+   *iterable*.  :class:`frozenset` is a built-in class.  See also
    :ref:`types-set` for documentation about this class.
 
    For other containers see the built-in :class:`set`, :class:`list`,
@@ -1814,7 +1814,7 @@ are always available.  They are listed here in alphabetical order.
    :noindex:
 
    Return a new :class:`set` object, optionally with elements taken from
-   *iterable*.  ``set`` is a built-in class.  See :class:`set` and
+   *iterable*.  :class:`set` is a built-in class.  See also
    :ref:`types-set` for documentation about this class.
 
    For other containers see the built-in :class:`frozenset`, :class:`list`,

Doc/library/unittest.mock.rst

@@ -2539,7 +2539,7 @@ Alternatively you can just use ``vars(my_mock)`` (instance members) and
 mock_open
 ~~~~~~~~~
 
-.. function:: mock_open(mock=None, read_data=None)
+.. function:: mock_open(mock=None, read_data='')
 
    A helper function to create a mock to replace the use of :func:`open`. It works
    for :func:`open` called directly or used as a context manager.

Lib/base64.py

@@ -1,4 +1,4 @@
-"""Base16, Base32, Base64 (RFC 3548), Base85 and Ascii85 data encodings"""
+"""Base16, Base32, Base64 (RFC 4648), Base85 and Ascii85 data encodings"""
 
 # Modified 04-Oct-1995 by Jack Jansen to use binascii module
 # Modified 30-Dec-2003 by Barry Warsaw to add full RFC 3548 support
@@ -219,7 +219,7 @@ def urlsafe_b64decode(s, *, padded=False):
 characters present in the input.
 '''
 _B32_DECODE_MAP01_DOCSTRING = '''
-RFC 3548 allows for optional mapping of the digit 0 (zero) to the
+RFC 4648 allows for optional mapping of the digit 0 (zero) to the
 letter O (oh), and for optional mapping of the digit 1 (one) to
 either the letter I (eye) or letter L (el).  The optional argument
 map01 when not None, specifies which letter the digit 1 should be
@@ -266,7 +266,7 @@ def b32hexdecode(s, casefold=False, *, padded=True, ignorechars=b'',
                                                     extra_args='')
 
 
-# RFC 3548, Base 16 Alphabet specifies uppercase, but hexlify() returns
+# RFC 4648, Base 16 Alphabet specifies uppercase, but hexlify() returns
 # lowercase.  The RFC also recommends against accepting input case
 # insensitively.
 def b16encode(s, *, wrapcol=0):

Lib/concurrent/futures/process.py

@@ -469,11 +469,9 @@ def _terminate_broken(self, cause):
             executor._shutdown_thread = True
             executor = None
 
-        # All pending tasks are to be marked failed with the following
-        # BrokenProcessPool error
-        bpe = BrokenProcessPool("A process in the process pool was "
-                                "terminated abruptly while the future was "
-                                "running or pending.")
+        # All pending tasks are to be marked failed with a
+        # BrokenProcessPool error, as separate instances to avoid sharing
+        # a traceback (gh-101267).
         cause_str = None
         if cause is not None:
             cause_str = ''.join(cause)
@@ -489,11 +487,15 @@ def _terminate_broken(self, cause):
                                   f"with exit code {p.exitcode}")
             if errors:
                 cause_str = "\n".join(errors)
-        if cause_str:
-            bpe.__cause__ = _RemoteTraceback(f"\n'''\n{cause_str}'''")
+        cause_tb = f"\n'''\n{cause_str}'''" if cause_str else None
 
         # Mark pending tasks as failed.
         for work_id, work_item in self.pending_work_items.items():
+            bpe = BrokenProcessPool("A process in the process pool was "
+                                    "terminated abruptly while the future was "
+                                    "running or pending.")
+            if cause_tb is not None:
+                bpe.__cause__ = _RemoteTraceback(cause_tb)
             try:
                 work_item.future.set_exception(bpe)
             except _base.InvalidStateError:

Lib/test/test_capi/test_unicode.py

@@ -842,16 +842,18 @@ def test_fromwidechar(self):
         if SIZEOF_WCHAR_T == 2:
             self.assertEqual(fromwidechar('a\U0001f600'.encode(encoding), 2), 'a\ud83d')
 
-        self.assertRaises(MemoryError, fromwidechar, b'', PY_SSIZE_T_MAX)
         self.assertRaises(SystemError, fromwidechar, b'\0'*SIZEOF_WCHAR_T, -2)
-        self.assertRaises(SystemError, fromwidechar, b'\0'*SIZEOF_WCHAR_T, PY_SSIZE_T_MIN)
         self.assertEqual(fromwidechar(NULL, 0), '')
         self.assertRaises(SystemError, fromwidechar, NULL, 1)
         self.assertRaises(SystemError, fromwidechar, NULL, PY_SSIZE_T_MAX)
         self.assertRaises(SystemError, fromwidechar, NULL, -1)
         self.assertRaises(SystemError, fromwidechar, NULL, -2)
         self.assertRaises(SystemError, fromwidechar, NULL, PY_SSIZE_T_MIN)
 
+        # The following tests are skipped since they rely on undefined behavior
+        #self.assertRaises(MemoryError, fromwidechar, b'', PY_SSIZE_T_MAX)
+        #self.assertRaises(SystemError, fromwidechar, b'\0'*SIZEOF_WCHAR_T, PY_SSIZE_T_MIN)
+
     @support.cpython_only
     @unittest.skipIf(_testlimitedcapi is None, 'need _testlimitedcapi module')
     def test_aswidechar(self):

Lib/test/test_concurrent_futures/test_process_pool.py

@@ -3,6 +3,7 @@
 import sys
 import threading
 import time
+import traceback
 import unittest
 import unittest.mock
 from concurrent import futures
@@ -62,6 +63,32 @@ def test_killed_child(self):
         # Submitting other jobs fails as well.
         self.assertRaises(BrokenProcessPool, self.executor.submit, pow, 2, 8)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
+    def test_broken_process_pool_traceback(self):
+        # When a child process is abruptly terminated, the whole pool gets
+        # "broken", and a BrokenProcessPool exception should be created
+        # for each future instead of sharing one exception among all futures.
+        event = self.create_event()
+        futures = [self.executor.submit(event.wait) for _ in range(3)]
+        p = next(iter(self.executor._processes.values()))
+        p.terminate()
+        for fut in futures:
+            # Don't use assertRaises(): it clears the traceback off exc.
+            try:
+                fut.result()
+            except BrokenProcessPool as exc:
+                tb = exc.__traceback__
+            else:
+                self.fail("BrokenProcessPool not raised")
+            count = sum(
+                1
+                for frame_summary in traceback.extract_tb(tb)
+                if frame_summary.filename == __file__
+            )
+            # This code file should appear exactly once in the traceback.
+            # A shared exception would accumulate a frame per result() call.
+            self.assertEqual(count, 1)
+
     @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     def test_map_chunksize(self):
         def bad_map():

Misc/ACKS

@@ -1762,6 +1762,7 @@ Charlie Shepherd
 Bruce Sherwood
 Gregory Shevchenko
 Hai Shi
+Daniel Shields
 Alexander Shigin
 Pete Shinners
 Michael Shiplett