3.2.2

3.2.2 (2025-11-30)

==================

Features added
--------------

* The C-API declarations were updated to include the new ``PyDict_*Ref()`` functions.
  (Github issue :issue:`7291`)

Bugs fixed
----------

* Iteration over literal sequences and strings in generators generated invalid C code since 3.2.0.
  This was a regression due to the C array iteration optimisation in :issue:`6926`, which is now
  disabled inside of generators.
  (Github issue :issue:`7342`)

* Calling special methods of known exception types failed with an ``AttributeError``.
  (Github issue :issue:`7342`)

* Calling the unbound ``__mul__`` special method of builtin collections with subtypes failed.
  (Github issue :issue:`7340`)

* C string literals could generate invalid "const to non-const" casts in the C code.
  (Github issue :issue:`7346`)

* ``yield`` is no longer allowed inside of a ``cython.critical_section``,
  but *is* now allowed while holding a ``cython.pymutex``.
  (Github issue :issue:`7317`)

* Under lock congestion, acquiring the GIL could crash in Python 3.11, part 2.
  This bug was introduced in Cython 3.2.0.
  (Github issue :issue:`7312`)

* The new ``py_safe_*`` functions in ``libc.threads`` triggered C compiler warnings.
  (Github issue :issue:`7356`)

3.2.1

3.2.1 (2025-11-12)

==================

Features added
--------------

* Cython now leaves markers about its utility code dependencies in the generated C code
  to help debugging "unused function" C compiler warnings.
  (Github issue :issue:`7294`)

Bugs fixed
----------

* Relative imports could fail if the shared utility module is used.
  This bug was introduces in Cython 3.2.0.
  (Github issue :issue:`7290`)

* Under lock congestion, acquiring the GIL could crash in Python 3.11.
  This bug was introduces in Cython 3.2.0.
  (Github issue :issue:`7312`)

* Using the shared utility module left an unused C function in user modules with memoryviews.
  To make debugging this kind of issue easier, Cython now leaves "used by …" markers in the
  generated C files that indicate why a specific piece of utility code was included.
  This bug was introduces in Cython 3.2.0.
  (Github issue :issue:`7293`)

* Code using the pre-import scope failed with an undefined name.
  This bug was introduces in Cython 3.2.0.
  (Github issue :issue:`7304`)

* Includes all fixes as of Cython 3.1.7.

3.1.7

3.1.7 (2025-11-12)

==================

Bugs fixed
----------

* Unicode characters formatted from C integers with padding, as in ``f"{value:XXc}"``,
  could result in invalid Python string objects since Cython 3.1.0.
  Also, lone surrogates failed to format in this way.
  (Github issue :issue:`7298`)

* Assigning nested structs from a list of structs (item by item) could crash Cython.
  (Github issue :issue:`7308`)

* Cython incorrectly called ``PyList_GetItemRef()`` in PyPy and GraalPython before Py3.13.
  (Github issue :issue:`7269`)

* Trying to instantiate internal types used by Cython is now prohibited.
  (Github issue :issue:`7263`)

3.2.0

3.2.0 (2025-11-05)

(Complete changelog for the 3.2.0 release, including pre-releases.)

Features added

• Builtin exception types are now inferred.
  (Github issue :issue:6908)

• The list of known, inferred and optimised Python builtins was updated.
  range is now considered a type. ascii, bin, format, hex, oct were added as functions.
  (Github issue :issue:6931)

• The f-string syntax was extended according to PEP-701.
  (Github issue :issue:5452)

• t-strings are implemented according to PEP-750. The implementation backports the template classes
  but prefers existing backports if installed separately.
  (Github issue :issue:6811)

• Unknown return type annotations with -> are no longer rejected but produce warnings.
  This allows better integration with Python type hints that are not always usable for Cython.
  -> None is also allowed now.
  Patch by jpe. (Github issue :issue:6946)

• The runtime Python dispatch for fused functions is substantially faster.
  (Github issues :issue:1385, :issue:6996)

• Freelists (via cdef class decorator and for internally used types such as async)
  are now also used in the Limited API and with extension type specs enabled.
  (Github issue :issue:7151)

• Module imports now quickly check for an already imported module to speed up reimports.
  Patch by Lysandros Nikolaou. (Github issue :issue:7035)

• Type checks on PEP-604 union types (int | None) are optimised into separate checks.
  (Github issue :issue:6935)

• Assignments to the PEP-604 union type float | None allow any suitable Python number as input
  and convert it to a Python float automatically.
  (Github issue :issue:5750)

• Item type inference was improved for looping over literals.
  (Github issue :issue:6912)

• Looping over literal sequences and strings now uses efficient C array looping if possible.
  (Github issue :issue:6926)

• Releasing the GIL from an unknown lock state is more efficient.
  (Github issue :issue:6847)

• cython.critical_section(PyMutex) now works, as with Python objects.
  (Github issue :issue:6847)

• bool(c_int/float/ptr) avoid passing through Python objects.
  (Github issue :issue:7015)

• Variables assigned inside of prange loops can now be initialised outside of the loop.
  (Github issue :issue:7178)

• Unused exceptions in except clauses are detected in some more cases to avoid their normalisation.
  (Github issue :issue:7021)

• Mixed operations on C integers with Python ints use less code and are more streamlined for Py3.12+.
  (Github issue :issue:7244)

• Some object constants are now marked as immortal to speed up their reference counting
  in recent CPython versions. This can be configured with the CYTHON_IMMORTAL_CONSTANTS C macro.
  (Github issue :issue:7118)

• Further improvements were made to reduce the size of the resulting extension modules.
  (Github issue :issue:6983, :issue:7199, :issue:7220, :issue:7238,
  :issue:7255, :issue:7265)

• Several improvements were made in freethreaded Python code.
  (Github issues :issue:6936, :issue:6939, :issue:6949, :issue:6984,
  :issue:7011, :issue:7066, :issue:7114, :issue:7200)

• Several improvements were made for the Limited API.
  (Github issues :issue:6959, :issue:6991)

• Several improvements were made for the GraalPython support.
  Patch by Michael Šimáček. (Github issue :issue:7074)

• Some GIL-safe C-API wrappers were added to the libc/libcpp declarations.
  (Github issue :issue:6829, :issue:6993)

• String and number constants use less storage space in the module.
  (Github issues :issue:6971, :issue:6978, :issue:6986)

• The managed dict/weakref support in CPython 3.12+ is used for internal types
  to benefit from future CPython optimisations here.
  (Github issue :issue:6891)

• Using NaN as exception return value is supported.
  (Github issues :issue:6900, :issue:6903)

• Declarations for C++ condition variables were added.
  (Github issue :issue:6836)

• The annotated source HTML page shows alternating +/− markers to open/close lines.
  Patch by Kamil Monicz. (Github issue :issue:7099)

• cython --embed gained a new option --embed-modules=… to list further extension modules
  that will be statically linked into the generated extension module, to get them initialised
  on application start.
  (Github issue :issue:2849)

• The setup.py script of Cython now allows passing the desired Limited API version
  like --cython-limited-api=3.11.
  (Github issue :issue:7228)

• Unicode 16.0.0 is used to parse identifiers.
  (Github issue :issue:6836)

Bugs fixed

• Special float exception values could generate invalid C code.
  (Github issues :issue:6900, :issue:6903)

• References to the Python bool type could generate invalid C code.
  (Github issue :issue:6902)

• Using cython.pymutex in an extension type declared as public or api
  generated invalid C code missing the required PyMutex declarations.
  (Github issues :issue:6992, :issue:6995)

• Cython's type sharing across modules suffered from race conditions if multiple modules
  tried to initialise and share their types concurrently. This is due to an underlying
  CPython issue and cannot easily be worked around completely. In the common case that
  module dicts are plain Python dict objects, however, Cython now uses a .setdefault()
  equivalent for thread-safe type sharing.
  See python/cpython#137422
  (Github issue :issue:7076)

• Cython incorrectly called PyList_GetItemRef() in PyPy and GraalPython before Py3.13.
  (Github issue :issue:7269)

• Iterating over temporary memoryviews could crash Cython.
  (Github issue :issue:7005)

• Type casts on constants as part of numeric expressions could crash Cython.
  (Github issue :issue:6779)

• Long code bodies in with statements could crash Cython.
  (Github issue :issue:7122)

• Vectorcalls could use needless temp assignments for self.
  (Github issue :issue:6909)

• Indexing bytes failed to optimise in some cases.
  (Github issue :issue:6997)

• Optimised C integer formatting in f-strings failed to apply to typedef types.
  (Github issue :issue:7170)

• In auto-pickling, trying to unpickle an object that has no __dict__ from object pickle data
  that includes instance dict state is now an error.
  (Github issue :issue:7222)

• The type objects of heap types were not always correctly decrefed on deallocation.
  (Github issue :issue:7145)

• Pure mode type aliases like p_int or ulong leaked into some C type contexts,
  risking to conflict with user declarations.
  (Github issues :issue:6922, :issue:6339)

• Boolean (emptyness) tests on builtin containers could fail to handle (unlikely) errors.
  (Github issue :issue:7090)

• The return type of bytes.join() was sometimes inferred as plain object.
  (Github issue :issue:6987)

• Type inference could fail to understand prange() arguments.
  (Github issue :issue:6974)

• embedsignatures failed if lambda was used in function default arguments.
  (Github issue :issue:6880)

• An internal C function was not marked as static and leaked a linker symbol.
  (Github issue :issue:6957)

• PyType_FromModuleAndSpec was incorrectly used in Limited API code before Py3.10.
  (Github issue :issue:7181)

• Conversion code for memoryview dtypes from and to Python objects generated C warnings about
  incorrect const / non-const casting code.
  (Github issue :issue:7219)

• Cython's tools and frontend scripts now use python3 instead of just python
  in their shebang line.
  Patch by Matti Picus. (Github issue :issue:7053)

• Extension arguments defined for the shared code module were ignored in cythonize().
  (Github issue :issue:7251)

• Failures while following package attributes in import pkg.module as … were not handled.

• Trying to instantiate internal types used by Cython is now prohibited.
  (Github issue :issue:7263)

• The setup.py script in the Demos/ subdirectory failed to build.
  (Github issue :issue:7228)

• The cygdb program failed to work with virtualenvs on Windows.
  Patch by Merlin. (Github issue :issue:7268)

• Includes all fixes as of Cython 3.1.6.

Other changes

• Some lesser used platforms (Windows ARM/i686, macOS x86_64, Linux i686, musllinux)
  now use Py3.9 abi3 binary wheels instead of Python version specific wheels.
  We also added an abi3 wheel for armv7l.
  (Github issues :issue:7227, :issue:7248, :issue:7250)

• Usages of Py_TPFLAGS_HAVE_FINALIZE were removed. The constant remains available as cimport from
  cpython.object for legacy reasons.
  (Github issue :issue:6423)

3.2.0b3

3.2.0b3 (2025-10-30)

====================

Bugs fixed
----------

* Using ``cython.pymutex`` in an extension type declared as ``public`` or ``api``
  generated invalid C code missing the required ``PyMutex`` declarations.
  (Github issues :issue:`6992`, :issue:`6995`)

* 3.2.0b2 generated incorrect pointer casts in the ``cimport`` importing code.
  (Github issue :issue:`7268`)

* Cython's type sharing across modules suffered from race conditions if multiple modules
  tried to initialise and share their types concurrently.  This is due to an underlying
  CPython issue and cannot easily be worked around completely.  In the common case that
  module dicts are plain Python dict objects, however, Cython now uses a ``.setdefault()``
  equivalent for thread-safe type sharing.
  See https://github.com/python/cpython/issues/137422
  (Github issue :issue:`7076`)

* Cython incorrectly called ``PyList_GetItemRef()`` in PyPy and GraalPython before Py3.13.
  (Github issue :issue:`7269`)

3.2.0b2

3.2.0b2 (2025-10-27)

====================

Features added
--------------

* The code generated for importing and exporting cimports across modules uses less space.
  (Github issues :issue:`7255`, :issue:`7265`)

Bugs fixed
----------

* Iteration over memoryviews could loop indefinitely in 3.2b1 when encountering a ``continue`` statement.
  (Github issue :issue:`7259`)

* Extension arguments defined for the shared code module were ignored in ``cythonize()``.
  (Github issue :issue:`7251`)

* Failures while following package attributes in ``import pkg.module as …`` were not handled.

* Trying to instantiate internal types used by Cython is now prohibited.
  (Github issue :issue:`7263`)

* Includes all fixes as of Cython 3.1.6.

Other changes
-------------

* The ``musllinux`` platform is now served with an abi3 Cython wheel instead of Python specific ones.
  (Github issue :issue:`7250`)

3.1.6

3.1.6 (2025-10-23)

==================

Bugs fixed
----------

* Unicode characters formatted from C integers with ``f"{value:c}"`` could result in
  invalid Python string objects since Cython 3.1.0.
  (Github issue :issue:`7240`)

* ``cythonize`` (program and function) now uses ``concurrent.futures.ProcessPoolExecutor``
  instead of ``multiprocessing.Pool`` to fix a hang on build failures in parallel builds.
  A possible work-around is to disable parallel builds.
  Patch by Sviatoslav Sydorenko.  (Github issue :issue:`7183`)

3.2.0b1-3

3.2.0b1 (2025-10-22)

====================

Features added
--------------

* Builtin exception types are now inferred.
  (Github issue :issue:`6908`)

* The list of known, inferred and optimised Python builtins was updated.
  `range` is now considered a type. `ascii`, `bin`, `format`, `hex`, `oct` were added as functions.
  (Github issue :issue:`6931`)

* The f-string syntax was extended according to PEP-701.
  (Github issue :issue:`5452`)

* t-strings are implemented according to PEP-750.  The implementation backports the template classes
  but prefers existing backports if installed separately.
  (Github issue :issue:`6811`)

* Unknown return type annotations with `->` are no longer rejected but produce warnings.
  This allows better integration with Python type hints that are not always usable for Cython.
  ``-> None``  is also allowed now.
  Patch by jpe.  (Github issue :issue:`6946`)

* The runtime Python dispatch for fused functions is substantially faster.
  (Github issues :issue:`1385`, :issue:`6996`)

* Freelists (via cdef class decorator and for internally used types such as ``async``)
  are now also used in the Limited API and with extension type specs enabled.
  (Github issue :issue:`7151`)

* Module imports now quickly check for an already imported module to speed up reimports.
  Patch by Lysandros Nikolaou.  (Github issue :issue:`7035`)

* Type checks on PEP-604 union types (`int | None`) are optimised into separate checks.
  (Github issue :issue:`6935`)

* Assignments to the PEP-604 union type `float | None` allow any suitable Python number as input
  and convert it to a Python `float` automatically.
  (Github issue :issue:`5750`)

* Item type inference was improved for looping over literals.
  (Github issue :issue:`6912`)

* Looping over literal sequences and strings now uses efficient C array looping if possible.
  (Github issue :issue:`6926`)

* Releasing the GIL from an unknown lock state is more efficient.
  (Github issue :issue:`6847`)

* ``cython.critical_section(PyMutex)`` now works, as with Python objects.
  (Github issue :issue:`6847`)

* ``bool(c_int/float/ptr)`` avoid passing through Python objects.
  (Github issue :issue:`7015`)

* Variables assigned inside of ``prange`` loops can now be initialised outside of the loop.
  (Github issue :issue:`7178`)

* Unused exceptions in ``except`` clauses are detected in some more cases to avoid their normalisation.
  (Github issue :issue:`7021`)

* Mixed operations on C integers with Python ints use less code and are more streamlined for Py3.12+.
  (Github issue :issue:`7244`)

* Some object constants are now marked as ``immortal`` to speed up their reference counting
  in recent CPython versions.  This can be configured with the ``CYTHON_IMMORTAL_CONSTANTS`` C macro.
  (Github issue :issue:`7118`)

* Further improvements were made to reduce the size of the resulting extension modules.
  (Github issue :issue:`6983`, :issue:`7199`, :issue:`7220`, :issue:`7238`)

* Several improvements were made in freethreaded Python code.
  (Github issues :issue:`6936`, :issue:`6939`, :issue:`6949`, :issue:`6984`,
  :issue:`7011`, :issue:`7066`, :issue:`7114`, :issue:`7200`)

* Several improvements were made for the Limited API.
  (Github issues :issue:`6959`, :issue:`6991`)

* Several improvements were made for the GraalPython support.
  Patch by Michael Šimáček.  (Github issue :issue:`7074`)

* Some GIL-safe C-API wrappers were added to the libc/libcpp declarations.
  (Github issue :issue:`6829`, :issue:`6993`)

* String and number constants use less storage space in the module.
  (Github issues :issue:`6971`, :issue:`6978`, :issue:`6986`)

* The managed dict/weakref support in CPython 3.12+ is used for internal types
  to benefit from future CPython optimisations here.
  (Github issue :issue:`6891`)

* Using ``NaN`` as exception return value is supported.
  (Github issues :issue:`6900`, :issue:`6903`)

* Declarations for C++ condition variables were added.
  (Github issue :issue:`6836`)

* The annotated source HTML page shows alternating +/− markers to open/close lines.
  Patch by Kamil Monicz.  (Github issue :issue:`7099`)

* ``cython --embed`` gained a new option ``--embed-modules=…`` to list further extension modules
  that will be statically linked into the generated extension module, to get them initialised
  on application start.
  (Github issue :issue:`2849`)

* The ``setup.py`` script of Cython now allows passing the desired Limited API version
  like ``--cython-limited-api=3.11``.
  (Github issue :issue:`7228`)

* Unicode 16.0.0 is used to parse identifiers.
  (Github issue :issue:`6836`)

Bugs fixed
----------

* Special float exception values could generate invalid C code.
  (Github issues :issue:`6900`, :issue:`6903`)

* References to the Python ``bool`` type could generate invalid C code.
  (Github issue :issue:`6902`)

* Unicode characters formatted from C integers with ``f"{value:c}"`` could result in
  invalid Python string objects since Cython 3.1.0.
  (Github issue :issue:`7240`)

* Vectorcalls could use needless temp assignments for ``self``.
  (Github issue :issue:`6909`)

* Iterating over temporary memoryviews could crash Cython.
  (Github issue :issue:`7005`)

* Type casts on constants as part of numeric expressions could crash Cython.
  (Github issue :issue:`6779`)

* Long code bodies in ``with`` statements could crash Cython.
  (Github issue :issue:`7122`)

* Indexing ``bytes`` failed to optimise in some cases.
  (Github issue :issue:`6997`)

* Optimised C integer formatting in f-strings failed to apply to typedef types.
  (Github issue :issue:`7170`)

* In auto-pickling, trying to unpickle an object that has no ``__dict__`` from object pickle data
  that includes instance dict state is now an error.
  (Github issue :issue:`7222`)

* The type objects of heap types were not always correctly decrefed on deallocation.
  (Github issue :issue:`7145`)

* Pure mode type aliases like ``p_int`` or ``ulong`` leaked into some C type contexts,
  risking to conflict with user declarations.
  (Github issues :issue:`6922`, :issue:`6339`)

* Boolean (emptyness) tests on builtin containers could fail to handle (unlikely) errors.
  (Github issue :issue:`7090`)

* The return type of ``bytes.join()`` was sometimes inferred as plain ``object``.
  (Github issue :issue:`6987`)

* Type inference could fail to understand ``prange()`` arguments.
  (Github issue :issue:`6974`)

* ``embedsignatures`` failed if ``lambda`` was used in function default arguments.
  (Github issue :issue:`6880`)

* An internal C function was not marked as ``static`` and leaked a linker symbol.
  (Github issue :issue:`6957`)

* ``PyType_FromModuleAndSpec`` was incorrectly used in Limited API code before Py3.10.
  (Github issue :issue:`7181`)

* Conversion code for memoryview dtypes from and to Python objects generated C warnings about
  incorrect ``const`` / non-``const``  casting code.
  (Github issue :issue:`7219`)

* ``cythonize`` (program and function) now uses ``concurrent.futures.ProcessPoolExecutor``
  instead of ``multiprocessing.Pool`` to fix a hang on build failures in parallel builds.
  A possible work-around is to disable parallel builds.
  Patch by Sviatoslav Sydorenko.  (Github issue :issue:`7183`)

* Cython's tools and frontend scripts now use ``python3``  instead of just ``python``
  in their shebang line.
  Patch by Matti Picus.  (Github issue :issue:`7053`)

* The ``setup.py`` script in the ``Demos/`` subdirectory failed to build.
  (Github issue :issue:`7228`)

* Includes all fixes as of Cython 3.1.5.

Other changes
-------------

* Usages of `Py_TPFLAGS_HAVE_FINALIZE` were removed.  The constant remains available as cimport from
  ``cpython.object`` for legacy reasons.
  (Github issue :issue:`6423`)

3.2.0b1

Not released due to package metadata problems.

3.1.5

3.1.5 (2025-10-19)

Bugs fixed

• Conversion from C++ strings longer than PY_SSIZE_T_MAX did not validate the length.

• Some non-Limited API code was incorrectly used in generated header files.
  (Github issue :issue:7157)

• Optimised unpacking of Python integers in expressions uses a slightly safer scheme.
  (Github issue :issue:7134)

• Empty return statements were not always reported when tracing.
  (Github issue :issue:7022)

• Value conversion errors when tracing C return statements no longer fail the trace
  but fall back to reporting None returns instead.
  (Github issue :issue:6503)