Sync pre-release CPython main branch from GitHub (2026-10-19)

Summary:
Imported python/cpython `3.16.0a1+dev` from upstream rev [`999855b`](https://www.github.com/python/cpython/commit/999855b07f9b795ca88ac3349060a06c116a1037) (committed 2026-10-19 04:46:36+00:00).

# Commit Info

- Base: (`3.16.0a1+dev`) - [`010bebb`](https://www.github.com/python/cpython/commit/010bebbf9fd12bba1e3f40bdbddacd51a9c2bf20) (commit date: 2026-10-17 03:24:12+00:00)
- Imported: (`3.16.0a1+dev`) - [`999855b`](https://www.github.com/python/cpython/commit/999855b07f9b795ca88ac3349060a06c116a1037) (commit date: 2026-10-19 04:46:36+00:00)

# Noteworthy file changes

- Low-signal files (7 added) (NEWS.d, docs, .github)

Complete list of added/removed files: https://www.internalfb.com/intern/everpaste/?color=0&handle=GLCFyzK-68s3fRkFANUd_690KDBKbr0LAAAz

Reviewed By: itamaro

Differential Revision: D126009430

fbshipit-source-id: 406e54a0982b45995d9a37fec580405a725635c2

Author: generatedunixname1734921407115435

.github/workflows/build.yml

@@ -491,53 +491,6 @@ jobs:
     if: fromJSON(needs.build-context.outputs.run-tests)
     uses: ./.github/workflows/reusable-test-lazy-imports-all.yml
 
-  build-asan:
-    name: 'Address sanitizer'
-    runs-on: ${{ matrix.os }}
-    timeout-minutes: 60
-    needs: build-context
-    if: needs.build-context.outputs.run-ubuntu == 'true'
-    strategy:
-      fail-fast: false
-      matrix:
-        os: [ubuntu-26.04]
-    env:
-      OPENSSL_VER: 3.5.9
-      PYTHONSTRICTEXTENSIONBUILD: 1
-      ASAN_OPTIONS: detect_leaks=0:allocator_may_return_null=1:handle_segv=0
-    steps:
-    - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-      with:
-        persist-credentials: false
-    - name: Runner image version
-      run: echo "IMAGE_OS_VERSION=${ImageOS}-${ImageVersion}" >> "$GITHUB_ENV"
-    - name: Register gcc problem matcher
-      run: echo "::add-matcher::.github/problem-matchers/gcc.json"
-    - name: Install dependencies
-      run: sudo ./.github/workflows/posix-deps-apt.sh
-    - name: Configure OpenSSL env vars
-      run: |
-        echo "MULTISSL_DIR=${GITHUB_WORKSPACE}/multissl" >> "$GITHUB_ENV"
-        echo "OPENSSL_DIR=${GITHUB_WORKSPACE}/multissl/openssl/${OPENSSL_VER}" >> "$GITHUB_ENV"
-        echo "LD_LIBRARY_PATH=${GITHUB_WORKSPACE}/multissl/openssl/${OPENSSL_VER}/lib" >> "$GITHUB_ENV"
-    - name: 'Restore OpenSSL build'
-      id: cache-openssl
-      uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
-      with:
-        path: ./multissl/openssl/${{ env.OPENSSL_VER }}
-        key: ${{ matrix.os }}-multissl-openssl-${{ env.OPENSSL_VER }}
-    - name: Install OpenSSL
-      if: steps.cache-openssl.outputs.cache-hit != 'true'
-      run: python3 Tools/ssl/multissltests.py --steps=library --base-directory "$MULTISSL_DIR" --openssl "$OPENSSL_VER" --system Linux
-    - name: Configure CPython
-      run: ./configure --config-cache --with-address-sanitizer --without-pymalloc --with-openssl="$OPENSSL_DIR"
-    - name: Build CPython
-      run: make -j4
-    - name: Display build info
-      run: make pythoninfo
-    - name: Tests
-      run: xvfb-run make ci
-
   build-san:
     # ${{ '' } is a hack to nest jobs under the same sidebar category.
     name: Sanitizers${{ '' }}  # zizmor: ignore[obfuscation]
@@ -554,6 +507,9 @@ jobs:
         sanitizer:
         - TSan
         include:
+        - check-name: Address
+          sanitizer: ASan
+          free-threading: false
         - check-name: Undefined behavior
           sanitizer: UBSan
           free-threading: false
@@ -667,7 +623,6 @@ jobs:
     - build-wasi
     - test-hypothesis
     - test-lazy-imports-all
-    - build-asan
     - build-san
     - cross-build-linux
     - cifuzz
@@ -714,7 +669,6 @@ jobs:
             build-ubuntu-installed,
             build-ubuntu-ssltests,
             test-hypothesis,
-            build-asan,
             build-san,
             cross-build-linux,
             '

.github/workflows/reusable-san.yml

@@ -43,6 +43,15 @@ jobs:
         # please update the versions in `Tools/pixi-packages/variants.yaml` too.
         echo "CC=clang" >> "$GITHUB_ENV"
         echo "CXX=clang++" >> "$GITHUB_ENV"
+    - name: ASan option setup
+      if: inputs.sanitizer == 'ASan'
+      run: |
+        echo "MULTISSL_DIR=${GITHUB_WORKSPACE}/multissl" >> "$GITHUB_ENV"
+        echo "OPENSSL_DIR=${GITHUB_WORKSPACE}/multissl/openssl/${OPENSSL_VER}" >> "$GITHUB_ENV"
+        echo "ASAN_OPTIONS=${SAN_LOG_OPTION} detect_leaks=0 allocator_may_return_null=1 handle_segv=0" >> "$GITHUB_ENV"
+        echo "PYTHONSTRICTEXTENSIONBUILD=1" >> "$GITHUB_ENV"
+      env:
+        SAN_LOG_OPTION: log_path=${{ github.workspace }}/san_log
     - name: TSan option setup
       if: inputs.sanitizer == 'TSan'
       run: |
@@ -88,24 +97,27 @@ jobs:
     - name: Add ccache to PATH
       run: |
         echo "PATH=/usr/lib/ccache:$PATH" >> "$GITHUB_ENV"
-    - name: 'Restore OpenSSL build (TSan)'
+    - name: 'Restore OpenSSL build'
       id: cache-openssl
-      if: inputs.sanitizer == 'TSan'
+      if: inputs.sanitizer == 'TSan' || inputs.sanitizer == 'ASan'
       uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
       with:
         path: ./multissl/openssl/${{ env.OPENSSL_VER }}
-        key: ${{ env.IMAGE_OS_VERSION }}-multissl-openssl-tsan-${{ env.OPENSSL_VER }}
-    - name: Install OpenSSL (TSan)
+        key: >-
+          ${{ env.IMAGE_OS_VERSION }}-multissl-openssl-${{
+            inputs.sanitizer == 'TSan' && 'tsan-' || ''
+          }}${{ env.OPENSSL_VER }}
+    - name: Install OpenSSL
       if: >-
-        inputs.sanitizer == 'TSan'
+        (inputs.sanitizer == 'TSan' || inputs.sanitizer == 'ASan')
         && steps.cache-openssl.outputs.cache-hit != 'true'
       run: >-
         python3 Tools/ssl/multissltests.py
         --steps=library
         --base-directory="${MULTISSL_DIR}"
         --openssl="${OPENSSL_VER}"
         --system=Linux
-        --tsan
+        ${{ inputs.sanitizer == 'TSan' && '--tsan' || '' }}
     # gh-157958: -O2 instead of the pydebug default -Og to avoid a clang 21
     # compile-time blowup on some interpreter files.
     # (https://github.com/llvm/llvm-project/issues/179695)
@@ -117,14 +129,20 @@ jobs:
         --config-cache
         OPT="-O2 -g"
         ${{
-          inputs.sanitizer == 'TSan'
+          inputs.sanitizer == 'ASan'
+          && '--with-address-sanitizer --without-pymalloc'
+          || inputs.sanitizer == 'TSan'
           && '--with-thread-sanitizer'
           || inputs.sanitizer == 'MSan'
           && '--with-memory-sanitizer'
           || '--with-undefined-behavior-sanitizer --with-strict-overflow'
         }}
         ${{ inputs.sanitizer == 'MSan' && '--with-assertions' || '--with-pydebug' }}
-        ${{ inputs.sanitizer == 'TSan' && '--with-openssl="$OPENSSL_DIR" --with-openssl-rpath=auto' || '' }}
+        ${{
+          (inputs.sanitizer == 'TSan' || inputs.sanitizer == 'ASan')
+          && '--with-openssl="$OPENSSL_DIR" --with-openssl-rpath=auto'
+          || ''
+        }}
         ${{ inputs.free-threading && '--disable-gil' || '' }}
     - name: Build CPython
       run: make -j4

Doc/library/dbm.rst

@@ -100,7 +100,8 @@ The :meth:`!setdefault` method requires two arguments.
 
 Key and values are always stored as :class:`bytes`. This means that when
 strings are used they are implicitly converted to the default encoding before
-being stored.
+being stored. For detailed information about accepted types, see
+:ref:`dbm-key-value-types`.
 
 These objects also support being used in a :keyword:`with` statement, which
 will automatically close them when done.
@@ -121,6 +122,47 @@ will automatically close them when done.
    :meth:`!clear` methods are now available for all :mod:`!dbm` backends.
 
 
+.. _dbm-key-value-types:
+
+Key and value types
+-------------------
+
+The accepted types for keys and values vary by backend. Keys and values are
+handled the same way, except where noted below:
+
+* **Traditional backends:**
+
+  * :mod:`dbm.gnu` and :mod:`dbm.ndbm`: Accept :class:`str` and :class:`bytes`
+    objects.
+  * :mod:`dbm.dumb`: Accepts :class:`str` and :class:`bytes` objects;
+    :class:`bytearray` is acceptable as a value, but not as a key.
+
+* **SQLite backend** (:mod:`dbm.sqlite3`): Accepts :class:`str`, :class:`bytes`,
+  :class:`int`, :class:`float`, :class:`bool`, :class:`bytearray`,
+  :class:`memoryview`, and :class:`array.array` objects.
+
+**Storage format:**
+
+All keys and values are stored as :class:`bytes` objects in the database.
+When retrieving, you'll always get bytes back, regardless of the original
+type stored.
+
+**Type conversion examples:**
+
+* ``db['key'] = 'string'`` stored as ``b'string'``
+* ``db['key'] = bytearray(b'data')`` stored as ``b'data'``
+  (:mod:`dbm.dumb` and :mod:`dbm.sqlite3` only)
+* ``db['key'] = 42`` stored as ``b'42'`` (:mod:`dbm.sqlite3` only)
+* ``db['key'] = 3.14`` stored as ``b'3.14'`` (:mod:`dbm.sqlite3` only)
+* ``db['key'] = True`` stored as ``b'1'`` (:mod:`dbm.sqlite3` only)
+* ``db['key'] = False`` stored as ``b'0'`` (:mod:`dbm.sqlite3` only)
+* ``db['key'] = memoryview(b'data')`` stored as ``b'data'``
+  (:mod:`dbm.sqlite3` only)
+* ``db['key'] = array.array('i', [1, 2, 3])`` stored as bytes (for example, on
+  little-endian: ``b'\x01\x00\x00\x00\x02\x00\x00\x00\x03\x00\x00\x00'``)
+  (:mod:`dbm.sqlite3` only)
+
+
 The following example records some hostnames and a corresponding title,  and
 then prints out the contents of the database::
 
@@ -142,8 +184,9 @@ then prints out the contents of the database::
        # Often-used methods of the dict interface work too.
        print(db.get('python.org', b'not present'))
 
-       # Storing a non-string key or value will raise an exception (most
-       # likely a TypeError).
+       # Storing a non-string key or value behavior depends on the backend:
+       # - Traditional backends (ndbm, gnu, dumb) will raise a TypeError
+       # - The sqlite3 backend accepts it and converts to bytes
        db['www.yahoo.com'] = 4
 
    # db is automatically closed when leaving the with statement.

Doc/library/mailbox.rst

@@ -15,6 +15,12 @@ accessing and manipulating on-disk mailboxes and the messages they contain.
 :class:`~email.message.Message` class with format-specific state and behavior.
 Supported mailbox formats are Maildir, mbox, MH, Babyl, and MMDF.
 
+.. warning::
+
+   The :mod:`!mailbox` module is designed for use in trusted environments,
+   where data from untrusted sources is never passed to the module's API
+   calls and only trusted users have access to the filesystems accessible
+   to the module.
 
 .. seealso::
 

Doc/library/traceback.rst

@@ -44,10 +44,6 @@ The module's API can be divided into two parts:
   necessary for later formatting without holding references to actual exception
   and traceback objects.
 
-.. versionadded:: 3.13
-   Output is colorized by default and can be
-   :ref:`controlled using environment variables <using-on-controlling-color>`.
-
 
 Module-Level Functions
 ----------------------

Include/errcode.h

@@ -38,6 +38,7 @@ extern "C" {
 #define E_BADSINGLE      27      /* Ill-formed single statement input */
 #define E_INTERACT_STOP  28      /* Interactive mode stopped tokenization */
 #define E_COLUMNOVERFLOW 29      /* Column offset overflow */
+#define E_INCOMPLETE     30      /* An unfinished token in partial input */
 
 #ifdef __cplusplus
 }

Include/internal/pycore_parser.h

@@ -27,13 +27,17 @@ _Py_DECLARE_STR(empty, "")
         }, \
     }
 
+/* The caller must initialize *incomplete to NULL if supplied. A returned AST
+   can also return an owned exception there for a missing line terminator.
+   Validate the AST before reporting that exception. */
 extern struct _mod* _PyParser_ASTFromString(
     const char *str,
     PyObject* filename,
     int mode,
     PyCompilerFlags *flags,
     PyArena *arena,
-    PyObject *module);
+    PyObject *module,
+    PyObject **incomplete);
 
 extern struct _mod* _PyParser_ASTFromFile(
     FILE *fp,

Lib/asyncio/base_events.py

@@ -1244,6 +1244,7 @@ async def _create_connection_transport(
             await waiter
         except:
             transport.close()
+            waiter = None
             raise
 
         return transport, protocol
@@ -1381,6 +1382,7 @@ async def start_tls(self, transport, protocol, sslcontext, *,
             transport.close()
             conmade_cb.cancel()
             resume_cb.cancel()
+            waiter = None
             raise
 
         return ssl_protocol._app_transport

Lib/asyncio/selector_events.py

@@ -1225,6 +1225,7 @@ def _call_connection_lost(self, exc):
             super()._call_connection_lost(exc)
         finally:
             self._write_ready = None
+            self._read_ready_cb = None
             if self._empty_waiter is not None:
                 self._empty_waiter.set_exception(
                     ConnectionError("Connection is closed by peer"))

Lib/codeop.py

@@ -62,15 +62,10 @@ def _maybe_compile(compiler, source, filename, symbol, flags):
         warnings.simplefilter("ignore", (SyntaxWarning, DeprecationWarning))
         try:
             compiler(source, filename, symbol, flags=flags)
+        except _IncompleteInputError:
+            return None
         except SyntaxError:  # Let other compile() errors propagate.
-            try:
-                compiler(source + "\n", filename, symbol, flags=flags)
-                return None
-            except _IncompleteInputError:
-                return None
-            except SyntaxError:
-                pass
-                # fallthrough
+            pass
 
     return compiler(source, filename, symbol, incomplete_input=False)