Merge branch 'main' into Optimize-_MATCH_CLASS

Author: savannahostrowski

Doc/c-api/init_config.rst

@@ -2299,13 +2299,91 @@ Py_GetArgcArgv()
 
    See also :c:member:`PyConfig.orig_argv` member.
 
-Delaying main module execution
-==============================
 
-In some embedding use cases, it may be desirable to separate interpreter initialization
-from the execution of the main module.
+Multi-Phase Initialization Private Provisional API
+==================================================
 
-This separation can be achieved by setting ``PyConfig.run_command`` to the empty
-string during initialization (to prevent the interpreter from dropping into the
-interactive prompt), and then subsequently executing the desired main module
-code using ``__main__.__dict__`` as the global namespace.
+This section is a private provisional API introducing multi-phase
+initialization, the core feature of :pep:`432`:
+
+* "Core" initialization phase, "bare minimum Python":
+
+  * Builtin types;
+  * Builtin exceptions;
+  * Builtin and frozen modules;
+  * The :mod:`sys` module is only partially initialized
+    (ex: :data:`sys.path` doesn't exist yet).
+
+* "Main" initialization phase, Python is fully initialized:
+
+  * Install and configure :mod:`importlib`;
+  * Apply the :ref:`Path Configuration <init-path-config>`;
+  * Install signal handlers;
+  * Finish :mod:`sys` module initialization (ex: create :data:`sys.stdout`
+    and :data:`sys.path`);
+  * Enable optional features like :mod:`faulthandler` and :mod:`tracemalloc`;
+  * Import the :mod:`site` module;
+  * etc.
+
+Private provisional API:
+
+.. c:member:: int PyConfig._init_main
+
+   If set to ``0``, :c:func:`Py_InitializeFromConfig` stops at the "Core"
+   initialization phase.
+
+.. c:function:: PyStatus _Py_InitializeMain(void)
+
+   Move to the "Main" initialization phase, finish the Python initialization.
+
+No module is imported during the "Core" phase and the ``importlib`` module is
+not configured: the :ref:`Path Configuration <init-path-config>` is only
+applied during the "Main" phase. It may allow to customize Python in Python to
+override or tune the :ref:`Path Configuration <init-path-config>`, maybe
+install a custom :data:`sys.meta_path` importer or an import hook, etc.
+
+It may become possible to calculate the :ref:`Path Configuration
+<init-path-config>` in Python, after the Core phase and before the Main phase,
+which is one of the :pep:`432` motivation.
+
+The "Core" phase is not properly defined: what should be and what should
+not be available at this phase is not specified yet. The API is marked
+as private and provisional: the API can be modified or even be removed
+anytime until a proper public API is designed.
+
+Example running Python code between "Core" and "Main" initialization
+phases::
+
+    void init_python(void)
+    {
+        PyStatus status;
+
+        PyConfig config;
+        PyConfig_InitPythonConfig(&config);
+        config._init_main = 0;
+
+        /* ... customize 'config' configuration ... */
+
+        status = Py_InitializeFromConfig(&config);
+        PyConfig_Clear(&config);
+        if (PyStatus_Exception(status)) {
+            Py_ExitStatusException(status);
+        }
+
+        /* Use sys.stderr because sys.stdout is only created
+           by _Py_InitializeMain() */
+        int res = PyRun_SimpleString(
+            "import sys; "
+            "print('Run Python code before _Py_InitializeMain', "
+                   "file=sys.stderr)");
+        if (res < 0) {
+            exit(1);
+        }
+
+        /* ... put more configuration code here ... */
+
+        status = _Py_InitializeMain();
+        if (PyStatus_Exception(status)) {
+            Py_ExitStatusException(status);
+        }
+    }

Doc/whatsnew/3.15.rst

@@ -1664,6 +1664,10 @@ New features
 * Add :c:func:`PyUnstable_SetImmortal` C-API function to mark objects as :term:`immortal`.
   (Contributed by Kumar Aditya in :gh:`143300`.)
 
+* Restore private provisional ``_Py_InitializeMain()`` function removed in
+  Python 3.14.
+  (Contributed by Victor Stinner in :gh:`142417`.)
+
 Changed C APIs
 --------------
 

Include/cpython/pylifecycle.h

@@ -25,6 +25,9 @@ PyAPI_FUNC(PyStatus) Py_PreInitializeFromArgs(
 PyAPI_FUNC(PyStatus) Py_InitializeFromConfig(
     const PyConfig *config);
 
+// Python 3.8 provisional API (PEP 587)
+PyAPI_FUNC(PyStatus) _Py_InitializeMain(void);
+
 PyAPI_FUNC(int) Py_RunMain(void);
 
 

Lib/test/test_embed.py

@@ -1319,6 +1319,24 @@ def test_init_run_main(self):
         }
         self.check_all_configs("test_init_run_main", config, api=API_PYTHON)
 
+    def test_init_main(self):
+        code = ('import _testinternalcapi, json; '
+                'print(json.dumps(_testinternalcapi.get_configs()))')
+        config = {
+            'argv': ['-c', 'arg2'],
+            'orig_argv': ['python3',
+                          '-c', code,
+                          'arg2'],
+            'program_name': './python3',
+            'run_command': code + '\n',
+            'parse_argv': True,
+            '_init_main': False,
+            'sys_path_0': '',
+        }
+        self.check_all_configs("test_init_main", config,
+                               api=API_PYTHON,
+                               stderr="Run Python code before _Py_InitializeMain")
+
     def test_init_parse_argv(self):
         config = {
             'parse_argv': True,

Lib/test/test_pyexpat.py

@@ -1069,7 +1069,9 @@ def test_set_maximum_amplification__amplification_not_exceeded(self):
         self.assertIsNotNone(parser.Parse(payload, True))
 
 
-@unittest.skipIf(expat.version_info < (2, 7, 2), "requires Expat >= 2.7.2")
+@unittest.skipIf(not hasattr(expat.XMLParserType,
+                             "SetAllocTrackerMaximumAmplification"),
+                 "requires Python compiled with Expat >= 2.7.2")
 class MemoryProtectionTest(AttackProtectionTestBase, unittest.TestCase):
 
     # NOTE: with the default Expat configuration, the billion laughs protection

Misc/NEWS.d/next/C_API/2026-03-03-14-59-57.gh-issue-142417.HiNP5j.rst

@@ -0,0 +1,2 @@
+Restore private provisional ``_Py_InitializeMain()`` function removed in
+Python 3.14. Patch by Victor Stinner.

Misc/NEWS.d/next/Tests/2026-02-12-12-12-00.gh-issue-144739.-fx1tN.rst

@@ -0,0 +1,3 @@
+When Python was compiled with system expat older then 2.7.2 but tests run
+with newer expat, still skip
+:class:`!test.test_pyexpat.MemoryProtectionTest`.

Modules/_functoolsmodule.c

@@ -252,6 +252,11 @@ partial_new(PyTypeObject *type, PyObject *args, PyObject *kw)
         }
         PyObject *item;
         PyObject *tot_args = PyTuple_New(tot_nargs);
+        if (tot_args == NULL) {
+            Py_DECREF(new_args);
+            Py_DECREF(pto);
+            return NULL;
+        }
         for (Py_ssize_t i = 0, j = 0; i < tot_nargs; i++) {
             if (i < npargs) {
                 item = PyTuple_GET_ITEM(pto_args, i);

Modules/timemodule.c

@@ -1170,7 +1170,8 @@ time_tzset(PyObject *self, PyObject *unused)
 
     /* Reset timezone, altzone, daylight and tzname */
     if (init_timezone(m) < 0) {
-         return NULL;
+        Py_DECREF(m);
+        return NULL;
     }
     Py_DECREF(m);
     if (PyErr_Occurred())

Objects/exceptions.c

@@ -912,7 +912,7 @@ BaseExceptionGroup_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 
     exceptions = PySequence_Tuple(exceptions);
     if (!exceptions) {
-        return NULL;
+        goto error;
     }
 
     /* We are now holding a ref to the exceptions tuple */