gh-136672: Docs: Move parts of Enum HOWTO to API Docs (GH-139176)
To avoid duplicate content in the Enum HOWTO and
API documentation which is not automatically synced,
the section about supported __dunder__ and _sunder
names is moved from HOWTO to API docs.
See also https://github.com/python/cpython/pull/136791
gh-142349: Fix refcount corruption in lazy import specialization (#144733)
Remove spurious Py_DECREF on borrowed ref in LOAD_GLOBAL specialization
_PyDict_LookupIndexAndValue() returns a borrowed reference via
_Py_dict_lookup(), but specialize_load_global_lock_held() called
Py_DECREF(value) on it when bailing out for lazy imports. Each time
the adaptive counter fired while a lazy import was still in globals,
this stole one reference from the dict's object. With 8+ threads
racing through LOAD_GLOBAL during concurrent lazy import resolution,
enough triggers accumulated to drive the refcount to zero while the
dict and other threads still referenced the object, causing
use-after-free.
Victor Stinner [Tue, 10 Feb 2026 19:31:12 +0000 (20:31 +0100)]
gh-141563: Fix test_cppext on macOS (#144685)
Don't test internal header files including mimalloc on macOS since
mimalloc emits compiler warnings:
In file included from extension.cpp:21:
In file included from Include/internal/pycore_backoff.h:15:
In file included from Include/internal/pycore_interp_structs.h:15:
In file included from Include/internal/pycore_tstate.h:14:
In file included from Include/internal/pycore_mimalloc.h:43:
Include/internal/mimalloc/mimalloc.h:464:85: error: defaulted
function definitions are a C++11 extension
[-Werror,-Wc++11-extensions]
mi_stl_allocator() mi_attr_noexcept = default;
^
Include/internal/mimalloc/mimalloc.h:465:85: error: defaulted
function definitions are a C++11 extension
[-Werror,-Wc++11-extensions]
mi_stl_allocator(const mi_stl_allocator&) mi_attr_noexcept = default;
Log also CXX and CXXFLAGS env vars in test_cppext. Log also CPPFLAGS
in test_cext.
Gregory P. Smith [Tue, 10 Feb 2026 13:08:33 +0000 (05:08 -0800)]
gh-143650: Fix importlib race condition on import failure (GH-143651)
Fix a race condition where a thread could receive a partially-initialized
module when another thread's import fails. The race occurs when:
1. Thread 1 starts importing, adds module to sys.modules
2. Thread 2 sees the module in sys.modules via the fast path
3. Thread 1's import fails, removes module from sys.modules
4. Thread 2 returns a stale module reference not in sys.modules
The fix adds verification after the "skip lock" optimization in both Python
and C code paths to check if the module is still in sys.modules. If the
module was removed (due to import failure), we retry the import so the
caller receives the actual exception from the import failure rather than
a stale module reference.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
gh-144563: Fix remote debugging with duplicate libpython mappings from ctypes (#144595)
When _ctypes is imported, it may call dlopen on the libpython shared
library, causing the dynamic linker to load a second mapping of the
library into the process address space. The remote debugging code
iterates memory regions from low addresses upward and returns the first
mapping whose filename matches libpython. After _ctypes is imported, it
finds the dlopen'd copy first, but that copy's PyRuntime section was
never initialized, so reading debug offsets from it fails.
Fix this by validating each candidate PyRuntime address before accepting
it. The validation reads the first 8 bytes and checks for the "xdebugpy"
cookie that is only present in an initialized PyRuntime. Uninitialized
duplicate mappings will fail this check and be skipped, allowing the
search to continue to the real, initialized PyRuntime.
Steve Dower [Tue, 10 Feb 2026 00:01:17 +0000 (00:01 +0000)]
gh-144278: Enable overriding sys.implementation's name and cache_tag when building sysmodule.c (GH-144293)
Changing the values requires forking and patching, which is intentional. Simply rebuilding from source does not change the implementation enough to justify changing these values - they would still be `cpython` and compatible with existing `.pyc` files. But people who maintain forks are better served by being able to easily override these values in a place that can be forward-ported reliably.
Petr Viktorin [Mon, 9 Feb 2026 10:35:43 +0000 (11:35 +0100)]
gh-140550: allow slots that repeat information from PyModuleDef (GH-144340)
When integrating slots-based module creation is with the inittab,
which currently requires PyModuleDef, it would be convenient to
reuse the the same slots array for the MethodDef.
Allow slots that match what's already present in the PyModuleDef.
Sam Gross [Fri, 6 Feb 2026 15:14:08 +0000 (10:14 -0500)]
gh-144513: Skip critical section locking during stop-the-world (gh-144524)
When the interpreter is in a stop-the-world pause, critical sections
don't need to acquire locks since no other threads can be running.
This avoids a potential deadlock where lock fairness hands off ownership
to a thread that has already suspended for stop-the-world.
kangtastic [Fri, 6 Feb 2026 14:43:16 +0000 (06:43 -0800)]
gh-101178: Add Ascii85, Base85, and Z85 support to binascii (GH-102753)
Add Ascii85, Base85, and Z85 encoders and decoders to binascii,
replacing the existing pure Python implementations in base64.
This makes the codecs two orders of magnitude faster and consume
two orders of magnitude less memory.
Note that attempting to decode Ascii85 or Base85 data of length 1 mod 5
(after accounting for Ascii85 quirks) now produces an error, as no
encoder would emit such data. This should be the only significant
externally visible difference compared to the old implementation.
Sam Gross [Fri, 6 Feb 2026 14:43:05 +0000 (09:43 -0500)]
gh-139103: Improve namedtuple scaling in free-threaded build (gh-144332)
Add `_Py_type_getattro_stackref`, a variant of type attribute lookup
that returns `_PyStackRef` instead of `PyObject*`. This allows returning
deferred references in the free-threaded build, reducing reference count
contention when accessing type attributes.
This significantly improves scaling of namedtuple instantiation across
multiple threads.
* Add blurb
* Rename PyObject_GetAttrStackRef to _PyObject_GetAttrStackRef
* Apply suggestion from @vstinner
Co-authored-by: Victor Stinner <vstinner@python.org>
* Apply suggestion from @vstinner
Co-authored-by: Victor Stinner <vstinner@python.org>
* format
* Update Include/internal/pycore_function.h
Co-authored-by: Victor Stinner <vstinner@python.org>
---------
Co-authored-by: Victor Stinner <vstinner@python.org>
Petr Viktorin [Fri, 6 Feb 2026 10:55:11 +0000 (11:55 +0100)]
gh-141004: Reorganize and reword the 'Useful macros' section (GH-144471)
- Group the macros
- Roughly order them to put the most important ones first
- Add expansions where it makes sense; especially if there's
an equivalent in modern C or a common compiler
Co-authored-by: Victor Stinner <vstinner@python.org> Co-authored-by: Peter Bierma <zintensitydev@gmail.com>
projects / thirdparty / Python / cpython.git / log
