Sync pre-release CPython 3.15 branch from GitHub (2026-07-18)

Summary:
Imported python/cpython `3.15.0b4+dev` from upstream rev [`13b29a9`](https://www.github.com/python/cpython/commit/13b29a98388505ecc72e30cd97b5c8b15b1ed751) (committed 2026-07-18 22:07:10+00:00).

# Commit Info

- Base: (`3.15.0b3+dev`) - [`4d74b76`](https://www.github.com/python/cpython/commit/4d74b76ed2534dfe74e085bcc0c86b2212838c6b) (commit date: 2026-07-18 00:01:13+00:00)
- Imported: (`3.15.0b4+dev`) - [`13b29a9`](https://www.github.com/python/cpython/commit/13b29a98388505ecc72e30cd97b5c8b15b1ed751) (commit date: 2026-07-18 22:07:10+00:00)

# Noteworthy file changes

- Test files (2 added)
- Low-signal files (4 added, 142 removed) (NEWS.d, docs, .github)

Complete list of added/removed files: https://www.internalfb.com/intern/everpaste/?color=0&handle=GMFK0CHK6tqjYboFAFU1dO3q-U8Wbr0LAAAz

Differential Revision: D112718830

fbshipit-source-id: 7d8225c157571fc84c5e9d2b7cc77dd93871bc04

Author: generatedunixname1734921407115435

Doc/c-api/exceptions.rst

@@ -499,12 +499,12 @@ Querying the error indicator
 .. c:function:: void PyErr_SetRaisedException(PyObject *exc)
 
    Set *exc* as the exception currently being raised,
-   clearing the existing exception if one is set.
+   clearing the existing exception if one is set.  If *exc* is ``NULL``,
+   just clear the existing exception.
 
-   .. warning::
+   *exc* must be a valid exception or ``NULL``.
 
-      This call ":term:`steals <steal>`" a reference to *exc*,
-      which must be a valid exception.
+   This call ":term:`steals <steal>`" a reference to *exc*.
 
    .. versionadded:: 3.12
 

Doc/c-api/frame.rst

@@ -243,3 +243,62 @@ Unless using :pep:`523`, you will not need this.
    Return the currently executing line number, or -1 if there is no line number.
 
    .. versionadded:: 3.12
+
+
+.. c:var:: const PyTypeObject *PyUnstable_ExecutableKinds
+
+   An array of executable kinds (executor types) for frames, used for internal
+   debugging and tracing.
+
+   Tools like debuggers and profilers can use this to identify the type of execution
+   context associated with a frame (such as to filter out internal frames).
+   The entries are indexed by the following constants:
+
+   .. list-table::
+      :header-rows: 1
+      :widths: auto
+
+      * - Constant
+        - Description
+      * - .. c:macro:: PyUnstable_EXECUTABLE_KIND_SKIP
+        - The frame is internal (For example: inlined) and should be skipped by tools.
+      * - .. c:macro:: PyUnstable_EXECUTABLE_KIND_PY_FUNCTION
+        - The frame corresponds to a standard Python function.
+      * - .. c:macro:: PyUnstable_EXECUTABLE_KIND_BUILTIN_FUNCTION
+        - The frame corresponds to a function defined in native code.
+      * - .. c:macro:: PyUnstable_EXECUTABLE_KIND_METHOD_DESCRIPTOR
+        - The frame corresponds to a method on a class instance.
+
+   However, Python's C API lacks a function to read the executable kind from
+   a frame. Instead, use this recipe:
+
+   .. code-block:: c
+
+      int
+      get_executable_kind(PyFrameObject *frame)
+      {
+         _PyInterpreterFrame *f = frame->f_frame;
+         PyObject *exec = PyStackRef_AsPyObjectBorrow(f->f_executable);
+
+         if (PyCode_Check(exec)) {
+            return PyUnstable_EXECUTABLE_KIND_PY_FUNCTION;
+         }
+         if (PyMethod_Check(exec)) {
+            return PyUnstable_EXECUTABLE_KIND_BUILTIN_FUNCTION;
+         }
+         if (Py_IS_TYPE(exec, &PyMethodDescr_Type)) {
+            return PyUnstable_EXECUTABLE_KIND_METHOD_DESCRIPTOR;
+         }
+
+         return PyUnstable_EXECUTABLE_KIND_SKIP;
+      }
+
+   .. versionadded:: 3.13
+
+
+.. c:macro:: PyUnstable_EXECUTABLE_KINDS
+
+   The number of entries in :c:data:`PyUnstable_ExecutableKinds`.
+
+   .. versionadded:: 3.13
+

Doc/c-api/veryhigh.rst

@@ -343,11 +343,125 @@ the same library that the Python runtime is using.
       :py:mod:`!ast` Python module, which exports these constants under
       the same names.
 
+   .. rubric:: Low-level flags
+
+   The following flags and masks serve narrow needs of the standard
+   library and interactive interpreters.  Code outside the standard
+   library rarely has a reason to use them.  They are considered
+   implementation details and may change at any time.
+
+   .. c:macro:: PyCF_ALLOW_INCOMPLETE_INPUT
+
+      This flag is a private interface between the compiler and the
+      :mod:`codeop` module.  Do not use it; its behavior is unsupported
+      and may change without warning.
+
+      With this flag set, when compilation fails because the source text
+      ends where more input is expected, for example in the middle of an
+      indented block or an unterminated string literal, the error raised
+      is the undocumented ``_IncompleteInputError``, a subclass of
+      :exc:`SyntaxError`.  The :mod:`codeop` module sets this flag,
+      together with :c:macro:`PyCF_DONT_IMPLY_DEDENT`, to tell input
+      that is incomplete apart from input with a real syntax error, so
+      that interactive interpreters know when to prompt for another
+      line instead of reporting an error.
+
+      .. versionadded:: 3.11
+
+   .. c:macro:: PyCF_DONT_IMPLY_DEDENT
+
+      By default, when compiling with the :c:var:`Py_single_input` start
+      symbol, reaching the end of the source text implicitly closes any
+      open indented blocks.  With this flag set, open blocks are only
+      closed if the last line of the source ends with a newline; otherwise,
+      compilation fails with a :exc:`SyntaxError`:
+
+      .. code-block:: c
+
+         PyCompilerFlags flags = {
+             .cf_flags = 0,
+             .cf_feature_version = PY_MINOR_VERSION,
+         };
+         const char *source = "if a:\n    pass";
+
+         /* The "if" block is closed implicitly;
+            this returns a code object: */
+         Py_CompileStringFlags(source, "<input>", Py_single_input, &flags);
+
+         /* With the flag, this fails with a SyntaxError,
+            because the last line does not end with a newline: */
+         flags.cf_flags = PyCF_DONT_IMPLY_DEDENT;
+         Py_CompileStringFlags(source, "<input>", Py_single_input, &flags);
+
+      The :mod:`codeop` module uses this flag to detect incomplete
+      interactive input.  While the user is still typing inside an
+      indented block, the source does not yet end with a newline, so it
+      fails to compile and the user is prompted for another line.
+
+   .. c:macro:: PyCF_IGNORE_COOKIE
+
+      Read the source text as UTF-8, ignoring its :pep:`263` encoding
+      declaration ("coding cookie"), if any:
+
+      .. code-block:: c
+
+         PyCompilerFlags flags = {
+             .cf_flags = 0,
+             .cf_feature_version = PY_MINOR_VERSION,
+         };
+         const char *source = "# coding: latin-1\ns = '\xe9'\n";
+
+         /* The coding cookie is honored: byte 0xE9 is decoded as
+            Latin-1, and this returns a code object that sets s to "é": */
+         Py_CompileStringFlags(source, "<input>", Py_file_input, &flags);
+
+         /* With the flag, the cookie is ignored and compilation fails
+            with a SyntaxError, because 0xE9 is not valid UTF-8: */
+         flags.cf_flags = PyCF_IGNORE_COOKIE;
+         Py_CompileStringFlags(source, "<input>", Py_file_input, &flags);
+
+      The :func:`compile`, :func:`eval` and :func:`exec` built-in functions
+      set this flag when the source is a :class:`str` object, because they
+      pass the text to the parser encoded as UTF-8.
+
+   .. c:macro:: PyCF_SOURCE_IS_UTF8
+
+      Mark the source text as known to be UTF-8 encoded.
+      The :func:`compile`, :func:`eval` and :func:`exec` built-in functions
+      set this flag, but it currently has no effect.
+
    The "``PyCF``" flags above can be combined with "``CO_FUTURE``" flags such
    as :c:macro:`CO_FUTURE_ANNOTATIONS` to enable features normally
    selectable using :ref:`future statements <future>`.
    See :ref:`c_codeobject_flags` for a complete list.
 
+   The following masks combine several flags:
+
+   .. c:macro:: PyCF_MASK
+
+      Bitmask of all ``CO_FUTURE`` flags (see :ref:`c_codeobject_flags`),
+      which select features normally enabled by
+      :ref:`future statements <future>`.
+      When code compiled with a ``PyCompilerFlags *flags`` argument
+      contains a ``from __future__ import`` statement, the flag for the
+      imported feature is added to *flags*, so that code executed later
+      in the same context inherits it.
+
+   .. c:macro:: PyCF_MASK_OBSOLETE
+
+      Do not use this mask in new code.  It is kept only so that old
+      code passing its flags to :func:`compile` keeps working.
+
+      Bitmask of flags for obsolete future features that no longer
+      have any effect.
+
+   .. c:macro:: PyCF_COMPILE_MASK
+
+      Bitmask of all ``PyCF`` flags that change how the source is
+      compiled, such as :c:macro:`PyCF_ONLY_AST`.
+      The :func:`compile` built-in function uses this mask to validate
+      its *flags* argument.
+
 
 .. _start-symbols:
 

Doc/library/asyncio-task.rst

@@ -377,7 +377,7 @@ and reliable way to wait for all tasks in the group to finish.
 
       * call it from the task group body based on some condition or event
       * pass the task group instance to child tasks via :meth:`create_task`, allowing a child
-        task to conditionally cancel the entire entire group
+        task to conditionally cancel the entire group
       * pass the task group instance or bound :meth:`cancel` method to some other task *before*
         opening the task group, allowing remote cancellation
 

Doc/library/calendar.rst

@@ -400,9 +400,9 @@ For simple text calendars this module provides the following functions.
    *month* (``1``--``12``), *day* (``1``--``31``).
 
 
-.. function:: weekheader(n)
+.. function:: weekheader(width)
 
-   Return a header containing abbreviated weekday names. *n* specifies the width in
+   Return a header containing abbreviated weekday names. *width* specifies the width in
    characters for one weekday.
 
 
@@ -430,12 +430,12 @@ For simple text calendars this module provides the following functions.
    of the :class:`TextCalendar` class.
 
 
-.. function:: prcal(year, w=0, l=0, c=6, m=3)
+.. function:: prcal(theyear, w=0, l=0, c=6, m=3)
 
    Prints the calendar for an entire year as returned by  :func:`calendar`.
 
 
-.. function:: calendar(year, w=2, l=1, c=6, m=3)
+.. function:: calendar(theyear, w=2, l=1, c=6, m=3)
 
    Returns a 3-column calendar for an entire year as a multi-line string using
    the :meth:`~TextCalendar.formatyear` of the :class:`TextCalendar` class.

Doc/library/concurrent.futures.rst

@@ -421,7 +421,7 @@ in a REPL or a lambda should not be expected to work.
       require the *fork* start method for :class:`ProcessPoolExecutor` you must
       explicitly pass ``mp_context=multiprocessing.get_context("fork")``.
 
-   .. versionchanged:: next
+   .. versionchanged:: 3.15
       Fixed a deadlock (:gh:`115634`) where the executor could hang after
       a worker process exited upon reaching its *max_tasks_per_child*
       limit while tasks remained queued.

Doc/library/concurrent.interpreters.rst

@@ -21,7 +21,7 @@ thread) and calling a function in that execution context.
 For concurrency, interpreters themselves (and this module) don't
 provide much more than isolation, which on its own isn't useful.
 Actual concurrency is available separately through
-:mod:`threads <threading>`  See `below <interp-concurrency_>`_
+:mod:`threads <threading>` -- see `below <interp-concurrency_>`_.
 
 .. seealso::
 

Doc/library/difflib.rst

@@ -85,6 +85,11 @@ diffs. For comparing directories and files, see also, the :mod:`filecmp` module.
    with inter-line and intra-line change highlights.  The table can be generated in
    either full or contextual difference mode.
 
+   .. warning::
+
+      The trailing newlines get stripped before the diff, so the result can be
+      incomplete. See :gh:`71896` for details.
+
    The constructor for this class is:
 
 

Doc/library/filecmp.rst

@@ -34,9 +34,9 @@ The :mod:`!filecmp` module defines the following functions:
    file changes.  The entire cache may be cleared using :func:`clear_cache`.
 
 
-.. function:: cmpfiles(dir1, dir2, common, shallow=True)
+.. function:: cmpfiles(a, b, common, shallow=True)
 
-   Compare the files in the two directories *dir1* and *dir2* whose names are
+   Compare the files in the two directories *a* and *b* whose names are
    given by *common*.
 
    Returns three lists of file names: *match*, *mismatch*,

Doc/library/functions.rst

@@ -611,9 +611,10 @@ are always available.  They are listed here in alphabetical order.
       untrusted user-supplied input will lead to security vulnerabilities.
 
    The *source* argument is parsed and evaluated as a Python expression
-   (technically speaking, a condition list) using the *globals* and *locals*
-   mappings as global and local namespace.  If the *globals* dictionary is
-   present and does not contain a value for the key ``__builtins__``, a
+   (technically speaking, an :ref:`expression list <exprlists>`)
+   using the *globals* and *locals* mappings as global and local namespace.
+   If the *globals* dictionary is present and does not contain a value for the
+   key ``__builtins__``, a
    reference to the dictionary of the built-in module :mod:`builtins` is
    inserted under that key before *source* is parsed.
    Overriding ``__builtins__`` can be used to restrict or change the available
@@ -633,6 +634,9 @@ are always available.  They are listed here in alphabetical order.
       >>> eval('x+1')
       2
 
+      >>> eval("1, 2")
+      (1, 2)
+
    This function can also be used to execute arbitrary code objects (such as
    those created by :func:`compile`).  In this case, pass a code object instead
    of a string.  If the code object has been compiled with ``'exec'`` as the