Sync pre-release CPython 3.15 branch from GitHub (2026-06-26)

Summary:
Imported python/cpython `3.15.0b3+dev` from upstream rev [`0290166`](https://www.github.com/python/cpython/commit/029016654ec08142f59d4f46113b3c1ec0830387) (committed 2026-06-26 23:31:46+00:00).

# Commit Info

- Base: (`3.15.0b3+dev`) - [`b7a4137`](https://www.github.com/python/cpython/commit/b7a41375ff9b247f53cc4264d4fe8a9fd45d8f7d) (commit date: 2026-06-26 03:49:15+00:00)
- Imported: (`3.15.0b3+dev`) - [`0290166`](https://www.github.com/python/cpython/commit/029016654ec08142f59d4f46113b3c1ec0830387) (commit date: 2026-06-26 23:31:46+00:00)

# Noteworthy file changes

- Low-signal files (9 added) (NEWS.d, docs, .github)

Complete list of added/removed files: https://www.internalfb.com/intern/everpaste/?color=0&handle=GDiXEyWDlCiYGXIDAJ-nIgZUa3Q6br0LAAAz

Differential Revision: D109921163

fbshipit-source-id: d2453dc519cdbda741f52ca335f3433ee32c8237

Author: generatedunixname1734921407115435

Doc/deprecations/soft-deprecations.rst

@@ -19,3 +19,8 @@ There are no plans to remove :term:`soft deprecated` APIs.
 
   (Contributed by Gregory P. Smith in :gh:`86519` and
   Hugo van Kemenade in :gh:`148100`.)
+
+* Using ``'F'`` and ``'D'`` format type codes of the :mod:`struct` module
+  now are :term:`soft deprecated` in favor of two-letter forms ``'Zf'``
+  and ``'Zd'``.
+  (Contributed by Sergey B Kirpichev in :gh:`121249`.)

Doc/library/struct.rst

@@ -260,10 +260,6 @@ platform-dependent.
 +--------+--------------------------+--------------------+----------------+------------+
 | ``d``  | :c:expr:`double`         | float              | 8              | \(4)       |
 +--------+--------------------------+--------------------+----------------+------------+
-| ``F``  | :c:expr:`float complex`  | complex            | 8              | \(10)      |
-+--------+--------------------------+--------------------+----------------+------------+
-| ``D``  | :c:expr:`double complex` | complex            | 16             | \(10)      |
-+--------+--------------------------+--------------------+----------------+------------+
 | ``Zf`` | :c:expr:`float complex`  | complex            | 8              | \(10)      |
 +--------+--------------------------+--------------------+----------------+------------+
 | ``Zd`` | :c:expr:`double complex` | complex            | 16             | \(10)      |
@@ -286,6 +282,7 @@ platform-dependent.
 
 .. versionchanged:: 3.15
    Added support for the ``'Zf'`` and ``'Zd'`` formats.
+   ``'F'`` and ``'D'`` formats are :term:`soft deprecated`.
 
 .. seealso::
 
@@ -376,13 +373,15 @@ Notes:
    are accepted.
 
 (10)
-   For the ``'F'`` and ``'D'`` format characters, the packed representation uses
+   For the ``'Zf'`` and ``'Zd'`` type codes, the packed representation uses
    the IEEE 754 binary32 and binary64 format for components of the complex
    number, regardless of the floating-point format used by the platform.
-   Note that complex types (``F``/``Zf`` and ``D``/``Zd``) are available unconditionally,
+   Note that complex types are available unconditionally,
    despite complex types being an optional feature in C.
    As specified in the C11 standard, each complex type is represented by a
    two-element C array containing, respectively, the real and imaginary parts.
+   The ``'F'`` and ``'D'`` (for ``'Zf'`` and ``'Zd'``, respectively) format
+   characters are supported for compatibility.
 
 
 A format character may be preceded by an integral repeat count.  For example,

Doc/whatsnew/3.15.rst

@@ -2280,6 +2280,11 @@ New deprecations
 
     (Contributed by Sergey B Kirpichev and Serhiy Storchaka in :gh:`143715`.)
 
+  * Using ``'F'`` and ``'D'`` type codes now are :term:`soft deprecated`
+    in favor of two-letter forms ``'Zf'`` and ``'Zd'``.
+    (Contributed by Sergey B Kirpichev in :gh:`121249`.)
+
+
 * :mod:`typing`:
 
   * The following statements now cause ``DeprecationWarning``\ s to be emitted

Lib/idlelib/idle_test/htest.py

@@ -216,9 +216,9 @@
     'file': 'browser',
     'kwds': {},
     'msg': textwrap.dedent("""
-        "Inspect names of module, class(with superclass if applicable),
-        "methods and functions.  Toggle nested items.  Double clicking
-        "on items prints a traceback for an exception that is ignored.""")
+        Inspect names of module, class(with superclass if applicable),
+        methods and functions.  Toggle nested items.  Double clicking
+        on items prints a traceback for an exception that is ignored.""")
     }
 
 _multistatus_bar_spec = {

Lib/test/support/__init__.py

@@ -35,7 +35,7 @@
     "requires_gil_enabled", "requires_linux_version", "requires_mac_ver",
     "check_syntax_error",
     "requires_gzip", "requires_bz2", "requires_lzma", "requires_zstd",
-    "bigmemtest", "bigaddrspacetest", "cpython_only", "get_attribute",
+    "bigmemtest", "nomemtest", "bigaddrspacetest", "cpython_only", "get_attribute",
     "requires_IEEE_754", "requires_zlib",
     "has_fork_support", "requires_fork",
     "has_subprocess_support", "requires_subprocess",
@@ -1314,6 +1314,22 @@ def wrapper(self):
         return wrapper
     return decorator
 
+def nomemtest(f):
+    """Check that we can use this test with `_testcapi.set_nomemory`."""
+    from .import_helper import import_module
+
+    @functools.wraps(f)
+    def internal(*args, **kwargs):
+        import_module('_testcapi')
+        return f(*args, **kwargs)
+
+    return unittest.skipIf(
+        # Python built with Py_TRACE_REFS fail with a fatal error in
+        # _PyRefchain_Trace() on memory allocation error.
+        Py_TRACE_REFS,
+        'cannot test Py_TRACE_REFS build',
+    )(cpython_only(internal))
+
 def bigaddrspacetest(f):
     """Decorator for tests that fill the address space."""
     def wrapper(self):

Lib/test/test_atexit.py

@@ -191,9 +191,7 @@ def callback():
         self.assertEqual(os.read(r, len(expected)), expected)
         os.close(r)
 
-    # Python built with Py_TRACE_REFS fail with a fatal error in
-    # _PyRefchain_Trace() on memory allocation error.
-    @unittest.skipIf(support.Py_TRACE_REFS, 'cannot test Py_TRACE_REFS build')
+    @support.nomemtest
     def test_atexit_with_low_memory(self):
         # gh-140080: Test that setting low memory after registering an atexit
         # callback doesn't cause an infinite loop during finalization.

Lib/test/test_capi/test_mem.py

@@ -117,9 +117,7 @@ def test_pyobject_forbidden_bytes_is_freed(self):
     def test_pyobject_freed_is_freed(self):
         self.check_pyobject_is_freed('check_pyobject_freed_is_freed')
 
-    # Python built with Py_TRACE_REFS fail with a fatal error in
-    # _PyRefchain_Trace() on memory allocation error.
-    @unittest.skipIf(support.Py_TRACE_REFS, 'cannot test Py_TRACE_REFS build')
+    @support.nomemtest
     def test_set_nomemory(self):
         code = """if 1:
             import _testcapi

Lib/test/test_class.py

@@ -449,7 +449,6 @@ def __delattr__(self, *args):
 
     def testHasAttrString(self):
         import sys
-        from test.support import import_helper
         _testlimitedcapi = import_helper.import_module('_testlimitedcapi')
 
         class A:
@@ -1013,11 +1012,8 @@ class C:
         C.a = X()
         C.a = X()
 
-    @cpython_only
+    @support.nomemtest
     def test_detach_materialized_dict_no_memory(self):
-        # Skip test if _testcapi is not available:
-        import_helper.import_module('_testcapi')
-
         code = """if 1:
             import test.support
             import _testcapi

Lib/test/test_dtrace.py

@@ -14,6 +14,10 @@
 
 if not support.has_subprocess_support:
     raise unittest.SkipTest("test module requires subprocess")
+if not sysconfig.get_config_var('WITH_DTRACE'):
+    raise unittest.SkipTest(
+        "CPython must be configured with the --with-dtrace option."
+    )
 
 
 def abspath(filename):
@@ -397,12 +401,9 @@ class BPFTraceOptimizedTests(TraceTests, unittest.TestCase):
 class CheckDtraceProbes(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        if sysconfig.get_config_var('WITH_DTRACE'):
-            readelf_major_version, readelf_minor_version = cls.get_readelf_version()
-            if support.verbose:
-                print(f"readelf version: {readelf_major_version}.{readelf_minor_version}")
-        else:
-            raise unittest.SkipTest("CPython must be configured with the --with-dtrace option.")
+        readelf_major_version, readelf_minor_version = cls.get_readelf_version()
+        if support.verbose:
+            print(f"readelf version: {readelf_major_version}.{readelf_minor_version}")
 
 
     @staticmethod

Lib/test/test_exceptions.py

@@ -1583,11 +1583,7 @@ def recurse_in_body_and_except():
             sys.setrecursionlimit(recursionlimit)
 
 
-    @cpython_only
-    # Python built with Py_TRACE_REFS fail with a fatal error in
-    # _PyRefchain_Trace() on memory allocation error.
-    @unittest.skipIf(support.Py_TRACE_REFS, 'cannot test Py_TRACE_REFS build')
-    @unittest.skipIf(_testcapi is None, "requires _testcapi")
+    @support.nomemtest
     def test_recursion_normalizing_with_no_memory(self):
         # Issue #30697. Test that in the abort that occurs when there is no
         # memory left and the size of the Python frames stack is greater than
@@ -1774,11 +1770,7 @@ def test_unhandled(self):
                     self.assertIn("test message", report)
                 self.assertEndsWith(report, "\n")
 
-    @cpython_only
-    # Python built with Py_TRACE_REFS fail with a fatal error in
-    # _PyRefchain_Trace() on memory allocation error.
-    @unittest.skipIf(support.Py_TRACE_REFS, 'cannot test Py_TRACE_REFS build')
-    @unittest.skipIf(_testcapi is None, "requires _testcapi")
+    @support.nomemtest
     def test_memory_error_in_PyErr_PrintEx(self):
         code = """if 1:
             import _testcapi
@@ -1936,12 +1928,8 @@ def test_keyerror_context(self):
             exc2 = None
 
 
-    @cpython_only
-    # Python built with Py_TRACE_REFS fail with a fatal error in
-    # _PyRefchain_Trace() on memory allocation error.
-    @unittest.skipIf(support.Py_TRACE_REFS, 'cannot test Py_TRACE_REFS build')
+    @support.nomemtest
     def test_exec_set_nomemory_hang(self):
-        import_module("_testcapi")
         # gh-134163: A MemoryError inside code that was wrapped by a try/except
         # block would lead to an infinite loop.