Merge in the main branch

Author: encukou

.github/CODEOWNERS

@@ -35,6 +35,7 @@ Objects/type*                 @markshannon
 Objects/codeobject.c          @markshannon
 Objects/frameobject.c         @markshannon
 Objects/call.c                @markshannon
+Objects/object.c              @ZeroIntensity
 Python/ceval*.c               @markshannon
 Python/ceval*.h               @markshannon
 Python/codegen.c              @markshannon @iritkatriel
@@ -66,8 +67,8 @@ Doc/_static/**                @AA-Turner @hugovk
 Doc/tools/**                  @AA-Turner @hugovk
 
 # runtime state/lifecycle
-**/*pylifecycle*              @ericsnowcurrently
-**/*pystate*                  @ericsnowcurrently
+**/*pylifecycle*              @ericsnowcurrently @ZeroIntensity
+**/*pystate*                  @ericsnowcurrently @ZeroIntensity
 **/*preconfig*                @ericsnowcurrently
 **/*initconfig*               @ericsnowcurrently
 **/*pathconfig*               @ericsnowcurrently

.github/workflows/build.yml

@@ -527,6 +527,14 @@ jobs:
       config_hash: ${{ needs.build-context.outputs.config-hash }}
       free-threading: ${{ matrix.free-threading }}
 
+  build-ubsan:
+    name: Undefined behavior sanitizer
+    needs: build-context
+    if: needs.build-context.outputs.run-tests == 'true'
+    uses: ./.github/workflows/reusable-ubsan.yml
+    with:
+      config_hash: ${{ needs.build-context.outputs.config-hash }}
+
   cross-build-linux:
     name: Cross build Linux
     runs-on: ubuntu-latest

.github/workflows/reusable-ubsan.yml

@@ -0,0 +1,74 @@
+name: Reusable Undefined Behavior Sanitizer
+
+on:
+  workflow_call:
+    inputs:
+      config_hash:
+        required: true
+        type: string
+
+env:
+  FORCE_COLOR: 1
+
+jobs:
+  build-ubsan-reusable:
+    name: 'Undefined behavior sanitizer'
+    runs-on: ubuntu-24.04
+    timeout-minutes: 60
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        persist-credentials: false
+    - name: Runner image version
+      run: echo "IMAGE_OS_VERSION=${ImageOS}-${ImageVersion}" >> "$GITHUB_ENV"
+    - name: Restore config.cache
+      uses: actions/cache@v4
+      with:
+        path: config.cache
+        key: ${{ github.job }}-${{ env.IMAGE_OS_VERSION }}-${{ inputs.config_hash }}
+    - name: Install dependencies
+      run: |
+        sudo ./.github/workflows/posix-deps-apt.sh
+        # Install clang-20
+        wget https://apt.llvm.org/llvm.sh
+        chmod +x llvm.sh
+        sudo ./llvm.sh 20
+    - name: UBSAN option setup
+      run: |
+        echo "UBSAN_OPTIONS=halt_on_error=1:abort_on_error=1:print_summary=1:print_stacktrace=1" >> "$GITHUB_ENV"
+        echo "CC=clang" >> "$GITHUB_ENV"
+        echo "CXX=clang++" >> "$GITHUB_ENV"
+    - name: Add ccache to PATH
+      run: |
+        echo "PATH=/usr/lib/ccache:$PATH" >> "$GITHUB_ENV"
+    - name: Configure ccache action
+      uses: hendrikmuhs/ccache-action@v1.2
+      with:
+        save: ${{ github.event_name == 'push' }}
+        max-size: "200M"
+    - name: Configure CPython
+      run: >-
+        ./configure
+        --config-cache
+        --with-undefined-behavior-sanitizer
+        --with-pydebug
+    - name: Set up UBSAN log after configuration
+      run: |
+        echo "UBSAN_OPTIONS=${UBSAN_OPTIONS}:log_path=${GITHUB_WORKSPACE}/ubsan_log" >> "$GITHUB_ENV"
+    - name: Build CPython
+      run: make -j4
+    - name: Display build info
+      run: make pythoninfo
+    - name: Tests
+      run: ./python -m test -j4
+    - name: Display UBSAN logs
+      if: always()
+      run: find "${GITHUB_WORKSPACE}" -name 'ubsan_log.*' | xargs head -n 1000
+    - name: Archive UBSAN logs
+      if: always()
+      uses: actions/upload-artifact@v4
+      with:
+        name: >-
+          ubsan-logs
+        path: ubsan_log.*
+        if-no-files-found: ignore

Doc/c-api/refcounting.rst

@@ -210,7 +210,7 @@ of Python objects.
 
         Py_SETREF(dst, src);
 
-   That arranges to set *dst* to *src* _before_ releasing the reference
+   That arranges to set *dst* to *src* *before* releasing the reference
    to the old value of *dst*, so that any code triggered as a side-effect
    of *dst* getting torn down no longer believes *dst* points
    to a valid object.

Doc/c-api/type.rst

@@ -282,6 +282,10 @@ Type Objects
    and other places where a method's defining class cannot be passed using the
    :c:type:`PyCMethod` calling convention.
 
+   The returned reference is :term:`borrowed <borrowed reference>` from *type*,
+   and will be valid as long as you hold a reference to *type*.
+   Do not release it with :c:func:`Py_DECREF` or similar.
+
    .. versionadded:: 3.11
 
 .. c:function:: int PyType_GetBaseByToken(PyTypeObject *type, void *token, PyTypeObject **result)

Doc/conf.py

@@ -79,6 +79,10 @@
 rst_epilog = f"""
 .. |python_version_literal| replace:: ``Python {version}``
 .. |python_x_dot_y_literal| replace:: ``python{version}``
+.. |python_x_dot_y_t_literal| replace:: ``python{version}t``
+.. |python_x_dot_y_t_literal_config| replace:: ``python{version}t-config``
+.. |x_dot_y_b2_literal| replace:: ``{version}.0b2``
+.. |applications_python_version_literal| replace:: ``/Applications/Python {version}/``
 .. |usr_local_bin_python_x_dot_y_literal| replace:: ``/usr/local/bin/python{version}``
 
 .. Apparently this how you hack together a formatted link:

Doc/data/refcounts.dat

@@ -2385,6 +2385,10 @@ PyType_GetFlags:PyTypeObject*:type:0:
 PyType_GetName:PyObject*::+1:
 PyType_GetName:PyTypeObject*:type:0:
 
+PyType_GetModuleByDef:PyObject*::0:
+PyType_GetModuleByDef:PyTypeObject*:type:0:
+PyType_GetModuleByDef:PyModuleDef*:def::
+
 PyType_GetQualName:PyObject*::+1:
 PyType_GetQualName:PyTypeObject*:type:0:
 

Doc/howto/free-threading-extensions.rst

@@ -6,8 +6,8 @@
 C API Extension Support for Free Threading
 ******************************************
 
-Starting with the 3.13 release, CPython has experimental support for running
-with the :term:`global interpreter lock` (GIL) disabled in a configuration
+Starting with the 3.13 release, CPython has support for running with
+the :term:`global interpreter lock` (GIL) disabled in a configuration
 called :term:`free threading`.  This document describes how to adapt C API
 extensions to support free threading.
 

Doc/howto/free-threading-python.rst

@@ -1,18 +1,21 @@
 .. _freethreading-python-howto:
 
-**********************************************
-Python experimental support for free threading
-**********************************************
+*********************************
+Python support for free threading
+*********************************
 
-Starting with the 3.13 release, CPython has experimental support for a build of
+Starting with the 3.13 release, CPython has support for a build of
 Python called :term:`free threading` where the :term:`global interpreter lock`
 (GIL) is disabled.  Free-threaded execution allows for full utilization of the
 available processing power by running threads in parallel on available CPU cores.
 While not all software will benefit from this automatically, programs
 designed with threading in mind will run faster on multi-core hardware.
 
-**The free-threaded mode is experimental** and work is ongoing to improve it:
-expect some bugs and a substantial single-threaded performance hit.
+The free-threaded mode is working and continues to be improved, but
+there is some additional overhead in single-threaded workloads compared
+to the regular build. Additionally, third-party packages, in particular ones
+with an :term:`extension module`, may not be ready for use in a
+free-threaded build, and will re-enable the :term:`GIL`.
 
 This document describes the implications of free threading
 for Python code.  See :ref:`freethreading-extensions-howto` for information on
@@ -43,7 +46,7 @@ Identifying free-threaded Python
 ================================
 
 To check if the current interpreter supports free-threading, :option:`python -VV <-V>`
-and :data:`sys.version` contain "experimental free-threading build".
+and :data:`sys.version` contain "free-threading build".
 The new :func:`sys._is_gil_enabled` function can be used to check whether
 the GIL is actually disabled in the running process.
 

Doc/library/concurrent.futures.rst

@@ -265,7 +265,7 @@ Each worker's interpreter is isolated from all the other interpreters.
 "Isolated" means each interpreter has its own runtime state and
 operates completely independently.  For example, if you redirect
 :data:`sys.stdout` in one interpreter, it will not be automatically
-redirected any other interpreter.  If you import a module in one
+redirected to any other interpreter.  If you import a module in one
 interpreter, it is not automatically imported in any other.  You
 would need to import the module separately in interpreter where
 you need it.  In fact, each module imported in an interpreter is
@@ -287,7 +287,7 @@ efficient alternative is to serialize with :mod:`pickle` and then send
 the bytes over a shared :mod:`socket <socket>` or
 :func:`pipe <os.pipe>`.
 
-.. class:: InterpreterPoolExecutor(max_workers=None, thread_name_prefix='', initializer=None, initargs=(), shared=None)
+.. class:: InterpreterPoolExecutor(max_workers=None, thread_name_prefix='', initializer=None, initargs=())
 
    A :class:`ThreadPoolExecutor` subclass that executes calls asynchronously
    using a pool of at most *max_workers* threads.  Each thread runs
@@ -304,32 +304,17 @@ the bytes over a shared :mod:`socket <socket>` or
    and *initargs* using :mod:`pickle` when sending them to the worker's
    interpreter.
 
-   .. note::
-      Functions defined in the ``__main__`` module cannot be pickled
-      and thus cannot be used.
-
    .. note::
       The executor may replace uncaught exceptions from *initializer*
       with :class:`~concurrent.futures.interpreter.ExecutionFailed`.
 
-   The optional *shared* argument is a :class:`dict` of objects that all
-   interpreters in the pool share.  The *shared* items are added to each
-   interpreter's ``__main__`` module.  Not all objects are shareable.
-   Shareable objects include the builtin singletons, :class:`str`
-   and :class:`bytes`, and :class:`memoryview`.  See :pep:`734`
-   for more info.
-
    Other caveats from parent :class:`ThreadPoolExecutor` apply here.
 
 :meth:`~Executor.submit` and :meth:`~Executor.map` work like normal,
 except the worker serializes the callable and arguments using
 :mod:`pickle` when sending them to its interpreter.  The worker
 likewise serializes the return value when sending it back.
 
-.. note::
-   Functions defined in the ``__main__`` module cannot be pickled
-   and thus cannot be used.
-
 When a worker's current task raises an uncaught exception, the worker
 always tries to preserve the exception as-is.  If that is successful
 then it also sets the ``__cause__`` to a corresponding