Sync pre-release CPython 3.15 branch from GitHub (2026-06-16)

Summary:
Imported python/cpython `3.15.0b2+dev` from upstream rev [`ff6e973`](https://www.github.com/python/cpython/commit/ff6e973c3bbe419ff8aef16b05a1c77749c073c2) (committed 2026-06-16 16:48:56+00:00).

# Commit Info

- Base: (`3.15.0b2+dev`) - [`e2c7fa7`](https://www.github.com/python/cpython/commit/e2c7fa7ff65dce05b857a3bbac275894dad967ad) (commit date: 2026-06-15 22:45:45+00:00)
- Imported: (`3.15.0b2+dev`) - [`ff6e973`](https://www.github.com/python/cpython/commit/ff6e973c3bbe419ff8aef16b05a1c77749c073c2) (commit date: 2026-06-16 16:48:56+00:00)

# Noteworthy file changes

- Test files (1 added)
- Low-signal files (2 added) (NEWS.d, docs, .github)

Complete list of added/removed files: https://www.internalfb.com/intern/everpaste/?color=0&handle=GKREQSuWsy43tWsFAH7VkD3Rxc8Sbr0LAAAz

Reviewed By: itamaro

Differential Revision: D108841492

fbshipit-source-id: 2ef85136c87396b057344a9d53513240b23418eb

Author: generatedunixname1734921407115435

Doc/c-api/init_config.rst

@@ -623,6 +623,10 @@ Some options are read from the :mod:`sys` attributes. For example, the option
 
    .. versionadded:: 3.14
 
+   .. versionchanged:: next
+      The function now replaces :data:`sys.flags` (create a new object),
+      instead of modifying :data:`sys.flags` in-place.
+
 
 .. _pyconfig_api:
 

Doc/c-api/module.rst

@@ -247,6 +247,15 @@ Feature slots
    If ``Py_mod_multiple_interpreters`` is not specified, the import
    machinery defaults to ``Py_MOD_MULTIPLE_INTERPRETERS_SUPPORTED``.
 
+   For historical reasons, the values are declared as pointers (``void *``).
+   When using :c:type:`PySlot` arrays, use :c:macro:`PySlot_DATA` for
+   :c:macro:`!Py_mod_multiple_interpreters`:
+
+   .. code-block:: c
+
+      PySlot_DATA(Py_mod_multiple_interpreters,
+                  Py_MOD_PER_INTERPRETER_GIL_SUPPORTED)
+
    .. versionadded:: 3.12
 
 .. c:macro:: Py_mod_gil
@@ -272,6 +281,14 @@ Feature slots
    If ``Py_mod_gil`` is not specified, the import machinery defaults to
    ``Py_MOD_GIL_USED``.
 
+   For historical reasons, the values are declared as pointers (``void *``).
+   When using :c:type:`PySlot` arrays, use :c:macro:`PySlot_DATA` for
+   :c:macro:`!Py_mod_gil`:
+
+   .. code-block:: c
+
+      PySlot_DATA(Py_mod_gil, Py_MOD_GIL_NOT_USED)
+
    .. versionadded:: 3.13
 
 

Lib/email/contentmanager.py

@@ -174,7 +174,8 @@ def set_text_content(msg, string, subtype="plain", charset='utf-8', cte=None,
                      params=None, headers=None):
     _prepare_set(msg, 'text', subtype, headers)
 
-    charset = email.charset.Charset(charset).input_charset
+    cs = email.charset.Charset(charset)
+    charset = cs.output_charset
     cte, payload = _encode_text(string, charset, cte, msg.policy)
     msg.set_payload(payload)
     msg.set_param('charset', charset, replace=True)

Lib/test/test_asyncio/test_ssl.py

@@ -1544,6 +1544,9 @@ async def client(addr):
             # This triggers bug gh-115514, also tested using mocks in
             # test.test_asyncio.test_selector_events.SelectorSocketTransportTests.test_write_buffer_after_close
             socket_transport = writer.transport._ssl_protocol._transport
+            # connection_lost may have already cleared _transport.
+            if socket_transport is None:
+                return
 
             class SocketWrapper:
                 def __init__(self, sock) -> None:

Lib/test/test_capi/test_config.py

@@ -356,9 +356,11 @@ def expect_bool_not(value):
                     for value in new_values:
                         expected, expect_flag = expect_func(value)
 
+                        old_flags = sys.flags
                         config_set(name, value)
                         self.assertEqual(config_get(name), expected)
                         self.assertEqual(getattr(sys.flags, sys_flag), expect_flag)
+                        self.assertIsNot(sys.flags, old_flags)
                         if name == "write_bytecode":
                             self.assertEqual(getattr(sys, "dont_write_bytecode"),
                                              expect_flag)

Lib/test/test_email/test_contentmanager.py

@@ -362,6 +362,46 @@ def test_set_text_charset_cp949(self):
         self.assertEqual(m.get_payload(decode=True), content.encode('ks_c_5601-1987'))
         self.assertEqual(m.get_content(), content)
 
+    def test_set_text_charset_shift_jis(self):
+        m = self._make_message()
+        content = "\u65e5\u672c\u8a9e\n"
+        raw_data_manager.set_content(m, content, charset='shift_jis')
+        self.assertEqual(m['Content-Type'], 'text/plain; charset="iso-2022-jp"')
+        self.assertEqual(m.get_payload(decode=True), content.encode('iso-2022-jp'))
+        self.assertEqual(m.get_content(), content)
+        self.assertEqual(str(m), textwrap.dedent("""\
+            Content-Type: text/plain; charset="iso-2022-jp"
+            Content-Transfer-Encoding: 7bit
+
+            \x1b$BF|K\\8l\x1b(B
+            """))
+        self.assertEqual(bytes(m), textwrap.dedent("""\
+            Content-Type: text/plain; charset="iso-2022-jp"
+            Content-Transfer-Encoding: 7bit
+
+            \u65e5\u672c\u8a9e
+            """).encode('iso-2022-jp'))
+
+    def test_set_text_charset_euc_jp(self):
+        m = self._make_message()
+        content = "\u65e5\u672c\u8a9e\n"
+        raw_data_manager.set_content(m, content, charset='euc-jp')
+        self.assertEqual(m['Content-Type'], 'text/plain; charset="iso-2022-jp"')
+        self.assertEqual(m.get_payload(decode=True), content.encode('iso-2022-jp'))
+        self.assertEqual(m.get_content(), content)
+        self.assertEqual(str(m), textwrap.dedent("""\
+            Content-Type: text/plain; charset="iso-2022-jp"
+            Content-Transfer-Encoding: 7bit
+
+            \x1b$BF|K\\8l\x1b(B
+            """))
+        self.assertEqual(bytes(m), textwrap.dedent("""\
+            Content-Type: text/plain; charset="iso-2022-jp"
+            Content-Transfer-Encoding: 7bit
+
+            \u65e5\u672c\u8a9e
+            """).encode('iso-2022-jp'))
+
     def test_set_text_plain_long_line_heuristics(self):
         m = self._make_message()
         content = ("Simple but long message that is over 78 characters"

Lib/test/test_free_threading/test_sys.py

@@ -0,0 +1,28 @@
+import sys
+import unittest
+from test.support import threading_helper
+
+
+class SysModuleTest(unittest.TestCase):
+    def test_int_max_str_digits_thread(self):
+        # gh-151218: Check that it's safe to call get_int_max_str_digits() and
+        # set_int_max_str_digits() in parallel. Previously, this test triggered
+        # warnings in TSan on a free threaded build.
+
+        old_limit = sys.get_int_max_str_digits()
+        self.addCleanup(sys.set_int_max_str_digits, old_limit)
+
+        def worker(worker_id):
+            if not worker_id:
+                for i in range (20_000):
+                    sys.get_int_max_str_digits()
+            else:
+                for i in range (20_000):
+                    sys.set_int_max_str_digits(4300 + (i & 7))
+
+        workers = [lambda: worker(i) for i in range(5)]
+        threading_helper.run_concurrently(workers)
+
+
+if __name__ == "__main__":
+    unittest.main()

Lib/test/test_os/test_posix.py

@@ -899,7 +899,9 @@ def check_stat(uid, gid):
             self.assertRaises(OSError, chown_func, first_param, 0, -1)
             check_stat(uid, gid)
             if hasattr(os, 'getgroups'):
-                if 0 not in os.getgroups():
+                # Also check the effective gid, which the kernel
+                # accepts for chown even if not in getgroups().
+                if 0 not in os.getgroups() and os.getegid() != 0:
                     self.assertRaises(OSError, chown_func, first_param, -1, 0)
                     check_stat(uid, gid)
         # test illegal types

Lib/test/test_sys.py

@@ -1359,6 +1359,26 @@ def test_pystats(self):
     def test_disable_gil_abi(self):
         self.assertEqual('t' in sys.abiflags, support.Py_GIL_DISABLED)
 
+    def test_int_max_str_digits(self):
+        old_limit = sys.get_int_max_str_digits()
+        self.assertIsInstance(old_limit, int)
+        self.assertGreaterEqual(old_limit, 0)
+        self.addCleanup(sys.set_int_max_str_digits, old_limit)
+
+        sys.set_int_max_str_digits(0)
+        self.assertEqual(sys.get_int_max_str_digits(), 0)
+
+        sys.set_int_max_str_digits(2_048)
+        self.assertEqual(sys.get_int_max_str_digits(), 2_048)
+
+        with self.assertRaises(ValueError):
+            # the minimum is 640 digits
+            sys.set_int_max_str_digits(5)
+        with self.assertRaises(ValueError):
+            sys.set_int_max_str_digits(-2)
+        with self.assertRaises(TypeError):
+            sys.set_int_max_str_digits(2_048.0)
+
 
 @test.support.cpython_only
 @test.support.force_not_colorized_test_class

Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-15-30-25.gh-issue-151218.5M_nv8.rst

@@ -0,0 +1,3 @@
+:c:func:`PyConfig_Set` and :func:`sys.set_int_max_str_digits` now replace
+:data:`sys.flags` (create a new object), instead of modifying :data:`sys.flags`
+in-place. Patch by Victor Stinner.