gh-142186: Revert the unintended value change in the `PY_MONITORING_EVENT_*` values from gh-146182 (gh-148955)
https://github.com/python/cpython/pull/146182 left an unintended change in the `PY_MONITORING_*` macro values. This change reverts that part to avoid a user visible impact.
Gregory P. Smith [Fri, 24 Apr 2026 16:36:46 +0000 (09:36 -0700)]
Improve `hash()` builtin docstring with caveats. (GH-125229)
Improve `hash()` builtin docstring with caveats.
Mention its return type and that the value can be expected to change between
processes (hash randomization).
Why? The `hash` builtin gets reached for and used by a lot of people whether it
is the right tool or not. IDEs surface docstrings and people use pydoc and
`help(hash)`.
Hai Zhu [Fri, 24 Apr 2026 09:37:01 +0000 (17:37 +0800)]
gh-146073: Add fitness/exit quality mechanism for JIT trace frontend (GH-148089)
* Replaces ad-hoc logic for ending traces with a simple inequality: `fitness < exit_quality`
* Fitness starts high and is reduced for branches, backward edges, calls and trace length
* Exit quality reflect how good a spot that instruction is to end a trace. Closing a loop is very, specializable instructions are very low and the others in between.
gh-145239: Accept unary plus literal pattern (#148566)
Add '+' alternatives to signed_number and signed_real_number grammar
rules, mirroring how unary minus is already handled for pattern matching.
Unary plus is a no-op on numbers so the value is returned directly without
wrapping in a UnaryOp node.
Sam Gross [Thu, 23 Apr 2026 18:42:57 +0000 (14:42 -0400)]
gh-113956: Make intern_common thread-safe in free-threaded build (gh-148886)
Avoid racing with the owning thread's refcount operations when
immortalizing an interned string: if we don't own it and its refcount
isn't merged, intern a copy we own instead. Use atomic stores in
_Py_SetImmortalUntracked so concurrent atomic reads are race-free.
Petr Viktorin [Thu, 23 Apr 2026 09:52:13 +0000 (11:52 +0200)]
gh-146636: Improve ABI/feature selection, add new header for it (GH-148302)
Improve ABI/feature selection, add new header for it.
Add a test that Python headers themselves don't use
Py_GIL_DISABLED in abi3t: abi3 and abi3t ought to be the
same except the _Py_OPAQUE_PYOBJECT differences.
This is done using the GCC-only poison pragma.
Co-authored-by: Victor Stinner <vstinner@python.org>
gh-119180: Document the `format` parameter in `typing.get_type_hints()` (#143758)
Do not mention `__annotations__` dictionaries, as this is slightly
outdated since 3.14.
Rewrite the note about possible exceptions for clarity. Also do not
mention imported type aliases, as since 3.12 aliases with the `type`
statement do not suffer from this limitation anymore.
John Seong [Thu, 23 Apr 2026 02:46:04 +0000 (10:46 +0800)]
gh-142965: Fix Concatenate documentation to reflect valid use cases (#143316)
The documentation previously stated that Concatenate is only valid
when used as the first argument to Callable, but according to PEP 612,
it can also be used when instantiating user-defined generic classes
with ParamSpec parameters.
Sam Gross [Wed, 22 Apr 2026 18:31:19 +0000 (14:31 -0400)]
gh-148820: Fix _PyRawMutex use-after-free on spurious semaphore wakeup (gh-148852)
_PyRawMutex_UnlockSlow CAS-removes the waiter from the list and then
calls _PySemaphore_Wakeup, with no handshake. If _PySemaphore_Wait
returns Py_PARK_INTR, the waiter can destroy its stack-allocated
semaphore before the unlocker's Wakeup runs, causing a fatal error from
ReleaseSemaphore / sem_post.
Loop in _PyRawMutex_LockSlow until _PySemaphore_Wait returns Py_PARK_OK,
which is only signalled when a matching Wakeup has been observed.
Also include GetLastError() and the handle in the Windows fatal messages
in _PySemaphore_Init, _PySemaphore_Wait, and _PySemaphore_Wakeup to make
similar races easier to diagnose in the future.
gh-142186: Allow all PEP-669 events to be per-code object and disableable (GH-146182)
* Make the `PY_UNWIND` monitoring event available as a code-local
event to allow trapping on function exit events when an exception
bubbles up. This complements the PY_RETURN event by allowing to
catch any function exit event.
* Allow `PY_UNWIND` to be `DISABLE`d; disabling it disables the event for the whole code object.
* Do the above for `PY_THROW`, `RAISE`, `EXCEPTION_HANDLED`, and `RERAISE` events.
Roman Donchenko [Mon, 20 Apr 2026 20:19:43 +0000 (23:19 +0300)]
gh-108411: Make typing.IO/BinaryIO arguments positional-only (#142906)
`IO` is purported to be the type of the file objects returned by `open`.
However, all methods on those objects take positional-only arguments, while
`IO`'s methods are declared with regular arguments. As such, the file objects
cannot actually be considered to implement `IO`. The same thing applies to
`BinaryIO`.
Fix this by adjusting the definition of these ABCs to match the file objects.
This is technically a breaking change, but it is unlikely to actually break
anything:
* These methods should never be called at runtime, since they are abstract.
Therefore, this should not cause any runtime errors.
* In typeshed these arguments are already positional-only, so this should
not cause any errors during typechecking either.
If _BlocksOutputBuffer_Finish() fails (memory allocation failure),
PyBytesWriter_Discard() is called on the writer. Then if
_BlocksOutputBuffer_OnError() is called, it calls again
PyBytesWriter_Discard() causing a double free.
Fix _BlocksOutputBuffer_Finish() by setting buffer->writer to NULL,
so _BlocksOutputBuffer_OnError() does nothing instead of calling
PyBytesWriter_Discard() again.
gh-148653: Fix some marshal errors related to recursive immutable objects (GH-148698)
Forbid marshalling recursive code, slice and frozendict objects which
cannot be correctly unmarshalled.
Reject invalid marshal data produced by marshalling recursive frozendict
objects which was previously incorrectly unmarshalled.
Add multiple tests for recursive data structures.
gh-148651: Fix refcount leak in _zstd decompressor options (#148657)
The option parsing in Modules/_zstd/decompressor.c had a missing Py_DECREF(value) before the early return -1 when PyLong_AsInt(key) fails. The identical code in Modules/_zstd/compressor.c line 158 has the fix.
Victor Stinner [Thu, 16 Apr 2026 17:13:25 +0000 (19:13 +0200)]
gh-148535: Don't use gcc -fprofile-update=atomic flag on i686 (#148554)
The -fprofile-update=atomic flag was added to fix a random GCC
internal error on PGO build (gh-145801) caused by corruption of
profile data (.gcda files). The problem is that it makes the PGO
build way slower (up to 47x slower) on i686. Since the GCC internal
error was not seen on i686 so far, don't use -fprofile-update=atomic
on i686.
Mark Shannon [Thu, 16 Apr 2026 14:33:09 +0000 (15:33 +0100)]
GH-146128: Fix AArch64 multi-instruction constants and relocations (GH-148598)
Fix AArch64 multi-instruction constants and relocations
* Elimates rendundant orr xN, xN, 0xffff after 16 or 32 bit loads
* Merges adrp (21rx) and ldr (12) relocations into single 33rx relocation, when safe to do so.
Mark Shannon [Thu, 16 Apr 2026 14:22:22 +0000 (15:22 +0100)]
GH-145668: Add FOR_ITER specialization for virtual iterators. Specialize GET_ITER. (GH-147967)
* Add FOR_ITER_VIRTUAL to specialize FOR_ITER for virtual iterators
* Add GET_ITER_SELF to specialize GET_ITER for iterators (including generators)
* Add GET_ITER_VIRTUAL to specialize GET_ITER for iterables as virtual iterators
* Add new (internal) _tp_iteritem function slot to PyTypeObject
* Put limited RESUME at start of genexpr for free-threading. Fix up exception handling in genexpr
gh-143886: Ensure function annotations are returned in order of definition (#143888)
Ensure function annotations are returned in order of definition
Previously, when getting type annotations of a function, normal
arguments were returned before positional-only ones in the dictionary.
Since `functools.singledispatch` relies on this ordering being correct
to dispatch based on the type of the first argument, this issue was
causing incorrect registrations for functions with positional-only
arguments.
This commit updates how annotations are generated so that
positional-only arguments are generated and added to the dictionary
before normal arguments.
This option changes the behavior of --enable-shared to continue to build
the libpython3.x.so shared library, but not use it for linking the
python3 interpreter executable. Instead, the executable is linked
directly against the libpython .o files as it would be with
--disable-shared.
There are two benefits of this change. First, libpython uses
thread-local storage, which is noticeably slower when used in a loaded
module instead of in the main program, because the main program can take
advantage of constant offsets from the thread state pointer but loaded
modules have to dynamically call a function __tls_get_addr() to
potentially allocate their thread-local storage area. (There is another
thread-local storage model for dynamic libraries which mitigates most of
this performance hit, but it comes at the cost of preventing
dlopen("libpython3.x.so"), which is a use case we want to preserve.)
Second, this improves the user experience around relocatable Python a
little bit, in that we don't need to use an $ORIGIN-relative path to
locate libpython3.x.so, which has some mild benefits around musl (which
does not support $ORIGIN-relative DT_NEEDED, only $ORIGIN-relative
DT_RPATH/DT_RUNPATH), users who want to make the interpreter setuid or
setcap (which prevents processing $ORIGIN), etc.