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Gregory P. Smith 64afa947f4
gh-146302: make Py_IsInitialized() thread-safe and reflect true init completion (GH-146303) 
## Summary

- Move the `runtime->initialized = 1` store from before `site.py` import to the end of `init_interp_main()`, so `Py_IsInitialized()` only returns true after initialization has fully completed
- Access `initialized` and `core_initialized` through new inline accessors using acquire/release atomics, to also protect from data race undefined behavior
- `PySys_AddAuditHook()` now uses the accessor, so with the flag move it correctly skips audit hook invocation during all init phases (matching the documented "after runtime initialization" behavior) ... We could argue that running these earlier would be good even if the intent was never explicitly expressed, but that'd be its own issue.

## Motivation

`Py_IsInitialized()` returned 1 while `Py_InitializeEx()` was still running — specifically, before `site.py` had been imported. See https://github.com/PyO3/pyo3/issues/5900 where a second thread could acquire the GIL and start executing Python with an incomplete `sys.path` because `site.py` hadn't finished.

The flag was also a plain `int` with no atomic operations, making concurrent reads a C-standard data race, though unlikely to manifest.

## Regression test:

The added test properly fails on `main` with `ERROR: Py_IsInitialized() was true during site import`.

---

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-04-11 21:54:23 +00:00
..
cpython gh-145921: Add "_DuringGC" functions for tp_traverse (GH-145925) 2026-04-08 09:15:11 +02:00
internal gh-146302: make Py_IsInitialized() thread-safe and reflect true init completion (GH-146303) 2026-04-11 21:54:23 +00:00
abstract.h gh-134989: Implement PyObject_DelAttr() as a macro in the limited C API (GH-135021) 2025-06-04 15:07:52 +02:00
audit.h gh-135755: Use private names (_Py*) for header file guards new in 3.14 (GH-135921) 2025-06-26 13:05:01 +02:00
bltinmodule.h
boolobject.h gh-134989: Fix Py_RETURN_NONE in the limited C API (GH-135165) 2025-06-05 14:43:47 +02:00
bytearrayobject.h gh-87347: Add parenthesis around PyXXX_Check() arguments (#92815) 2022-06-16 13:49:43 +02:00
bytesobject.h gh-108765: Move standard includes to Python.h (#108769) 2023-09-01 21:03:20 +02:00
ceval.h gh-135755: Move SPECIAL_ constants to a private header (GH-135922) 2025-06-25 13:03:05 +02:00
codecs.h Remove private _PyCodec_Lookup() function (#106269) 2023-06-30 09:34:01 +00:00
compile.h gh-109596: Ensure repeated rules in the grammar are not allowed and fix incorrect soft keywords (#109606) 2023-09-22 19:03:23 +01:00
complexobject.h gh-87347: Add parenthesis around PyXXX_Check() arguments (#92815) 2022-06-16 13:49:43 +02:00
critical_section.h gh-119344: Make critical section API public (#119353) 2024-06-21 15:50:18 -04:00
datetime.h gh-141563: Add missing cast to _PyDateTime_IMPORT() (#144667) 2026-02-10 14:47:12 +00:00
descrobject.h gh-41779: Allow defining any __slots__ for a class derived from tuple (GH-141763) 2026-01-06 11:36:00 +02:00
dictobject.h gh-141726: Add PyDict_SetDefaultRef() to the Stable ABI (#141727) 2025-11-19 11:38:10 +00:00
dynamic_annotations.h gh-96959: Update HTTP links which are redirected to HTTPS (GH-96961) 2022-09-24 14:38:53 +03:00
enumobject.h
errcode.h gh-107450: Check for overflow in the tokenizer and fix overflow test (#110832) 2023-10-16 16:42:49 +02:00
exports.h gh-141671: PyMODINIT_FUNC: apply __declspec(dllexport) on Windows (GH-141672) 2026-01-07 13:09:48 +01:00
fileobject.h gh-106320: Remove _PyIsSelectable_fd() C API (#107142) 2023-07-23 19:07:12 +00:00
fileutils.h gh-67341: fix a typo in Include/fileutils.h (#136049) 2025-07-14 08:02:05 +00:00
floatobject.h gh-141004: soft-deprecate Py_INFINITY macro (#141033) 2025-11-12 13:44:49 +01:00
frameobject.h bpo-45434: Remove useless space in includes (GH-28963) 2021-10-15 01:50:04 +02:00
genericaliasobject.h bpo-44654: Refactor and clean up the union type implementation (GH-27196) 2021-07-17 22:44:10 +03:00
import.h gh-142349: Fix build errors from PEP 810 (#144726) 2026-02-12 08:18:36 +00:00
intrcheck.h gh-106320: Remove private _PyOS_IsMainThread() function (#108605) 2023-08-29 03:20:31 +00:00
iterobject.h gh-106320: Remove _PyAnextAwaitable_Type from the public C API (#108597) 2023-08-29 02:05:11 +00:00
listobject.h gh-114329: Fix PyList_GetItemRef() limited C API definition (#117520) 2024-04-03 21:02:42 +00:00
longobject.h gh-143869: Add PEP 757 functions to the limited API (#143906) 2026-01-21 14:47:14 +01:00
marshal.h gh-79315: Add Include/cpython/marshal.h header (#139725) 2025-10-07 23:49:08 +02:00
memoryobject.h gh-79315: Add Include/cpython/memoryobject.h header (#99723) 2022-11-23 15:44:42 +01:00
methodobject.h gh-132097: use a macro for semantically casting function pointers (#132406) 2025-04-18 12:24:34 +02:00
modsupport.h gh-142225: Fix PyABIInfo_VAR macro (GH-142230) 2025-12-04 10:33:15 +01:00
moduleobject.h gh-145921: Add "_DuringGC" functions for tp_traverse (GH-145925) 2026-04-08 09:15:11 +02:00
object.h gh-145921: Add "_DuringGC" functions for tp_traverse (GH-145925) 2026-04-08 09:15:11 +02:00
objimpl.h gh-102013: Move PyUnstable_GC_VisitObjects() to Include/cpython/objimpl.h (#115560) 2024-02-16 15:49:13 +01:00
opcode.h gh-100239: replace BINARY_SUBSCR & family by BINARY_OP with oparg NB_SUBSCR (#129700) 2025-02-07 22:39:54 +00:00
opcode_ids.h GH-145667: Merge GET_ITER and GET_YIELD_FROM_ITER (GH-146120) 2026-03-21 10:48:13 +00:00
osdefs.h gh-108765: Reformat Include/osdefs.h (#108766) 2023-09-01 14:35:39 +00:00
osmodule.h Issue #29058: All stable API extensions added after Python 3.2 are now 2016-12-27 14:57:39 +02:00
patchlevel.h Post 3.15.0a8 2026-04-07 20:32:33 +03:00
py_curses.h gh-125843: indicate which C function caused a curses.error (#125844) 2025-05-19 15:53:39 +02:00
pyatomic.h gh-108724: Add PyMutex and _PyParkingLot APIs (gh-109344) 2023-09-19 09:54:29 -06:00
pybuffer.h gh-137696: Rename 'fort' parameter to 'order' in PyBuffer_* functions (#137866) 2026-03-19 16:54:27 +05:30
pycapsule.h gh-108240: Add pycore_capsule.h internal header file (#108596) 2023-08-29 01:20:02 +00:00
pydtrace.d bpo-36842: Implement PEP 578 (GH-12613) 2019-05-23 08:45:22 -07:00
pydtrace.h Fix pydtrace.d path comment in Include/pydtrace.h (#28539) 2022-12-31 22:40:25 +05:30
pyerrors.h gh-142349: Implement PEP 810 - Explicit lazy imports (#142351) 2026-02-12 00:15:33 +00:00
pyexpat.h gh-90949: expose Expat API to tune exponential expansion protections (#139368) 2025-09-28 08:27:04 +00:00
pyframe.h gh-93937, C API: Move PyFrame_GetBack() to Python.h (#93938) 2022-06-19 12:02:33 +02:00
pyhash.h gh-111545: Add Include/cpython/pyhash.h header file (#112063) 2023-11-15 01:19:20 +01:00
pylifecycle.h gh-133644: Remove deprecated Python initialization getter functions (#133661) 2025-05-09 11:39:23 +00:00
pymacconfig.h gh-145633: Remove support for ancient ARM platforms with mixed-endian doubles (#145634) 2026-03-11 12:39:24 +01:00
pymacro.h gh-141370: Fix undefined behavior when using Py_ABS() (GH-141548) 2025-12-05 16:24:35 +02:00
pymath.h gh-141004: soft-deprecate Py_INFINITY macro (#141033) 2025-11-12 13:44:49 +01:00
pymem.h gh-85283: Add PyMem_RawMalloc() to the limited C API (#108570) 2023-10-17 02:41:51 +02:00
pyport.h gh-146636: abi3t: Define Py_GIL_DISABLED but do not use it (GH-148142) 2026-04-07 09:06:17 +02:00
pystate.h gh-108867: Add PyThreadState_GetUnchecked() function (#108870) 2023-10-03 16:53:51 +00:00
pystats.h GH-124284: Add stats for refcount operations on immortal objects (GH-124288) 2024-09-23 19:10:55 +01:00
pystrcmp.h
pystrtod.h gh-106320: Remove private float C API functions (#108430) 2023-08-24 19:09:49 +02:00
Python.h gh-146636: PEP 803: add Py_TARGET_ABI3T and .abi3t.so extension (GH-146637) 2026-04-01 16:14:59 +02:00
pythonrun.h gh-130396: Move PYOS_LOG2_STACK_MARGIN to internal headers (#135928) 2025-07-01 15:18:17 +02:00
pythread.h gh-137884: Added threading.get_native_id() on Illumos/Solaris (GH-137927) 2025-08-20 17:10:44 +00:00
pytypedefs.h bpo-45459: Fix PyModuleDef_Slot type in the limited C API (GH-31668) 2022-03-03 23:06:55 +01:00
rangeobject.h gh-87347: Add parenthesis around PyXXX_Check() arguments (#92815) 2022-06-16 13:49:43 +02:00
README.rst gh-101101: Unstable C API tier (PEP 689) (GH-101102) 2023-02-28 09:31:01 +01:00
refcount.h gh-146636: abi3t: Define Py_GIL_DISABLED but do not use it (GH-148142) 2026-04-07 09:06:17 +02:00
setobject.h gh-87347: Add parenthesis around PyXXX_Check() arguments (#92815) 2022-06-16 13:49:43 +02:00
sliceobject.h gh-79315: Add Include/cpython/sliceobject.h header (#139729) 2025-10-08 00:48:18 +02:00
structmember.h Fix typos in comments (#120188) 2024-06-07 10:19:41 +02:00
structseq.h gh-79315: Add Include/cpython/structseq.h header (#139730) 2025-10-08 01:19:50 +02:00
sysmodule.h gh-138886: Remove deprecated PySys_ResetWarnOptions C-API function (#138887) 2025-09-15 12:01:33 +03:00
traceback.h gh-87347: Add parenthesis around PyXXX_Check() arguments (#92815) 2022-06-16 13:49:43 +02:00
tupleobject.h gh-87347: Add parenthesis around PyXXX_Check() arguments (#92815) 2022-06-16 13:49:43 +02:00
typeslots.h Revert "gh-133395: add option for extension modules to specialize BINARY_OP/SUBSCR, apply to arrays (#133396)" (#133498) 2025-05-06 13:12:26 +03:00
unicodeobject.h gh-146175: Soft-deprecate outdated macros; convert internal usage (GH-146178) 2026-03-23 12:42:09 +01:00
warnings.h bpo-35134: Split warnings.h and weakrefobject.h (GH-29042) 2021-10-19 01:31:57 +02:00
weakrefobject.h gh-133644: remove PyWeakref_GetObject and PyWeakref_GET_OBJECT (GH-133657) 2025-09-24 11:25:56 +02:00

README.rst 

The Python C API
================

The C API is divided into these sections:

1. ``Include/``: Limited API
2. ``Include/cpython/``: CPython implementation details
3. ``Include/cpython/``, names with the ``PyUnstable_`` prefix: API that can
   change between minor releases
4. ``Include/internal/``, and any name with ``_`` prefix: The internal API

Information on changing the C API is available `in the developer guide`_

.. _in the developer guide: https://devguide.python.org/c-api/