=================
Features added
--------------
* PEP-489 multi-phase module initialisation has been enabled again. Module
reloads in other subinterpreters raise an exception to prevent corruption
of the static module state.
* A set of ``mypy`` compatible PEP-484 declarations were added for Cython's C data
types to integrate with static analysers in typed Python code. They are available
in the ``Cython/Shadow.pyi`` module and describe the types in the special ``cython``
module that can be used for typing in Python code.
Original patch by Julian Gethmann. (Github issue 1965)
* Memoryviews are supported in PEP-484/526 style type declarations.
(Github issue 2529)
* ``cython.nogil`` is supported as a C-function decorator in Python code.
(Github issue 2557)
* Raising exceptions from nogil code will automatically acquire the GIL, instead
of requiring an explicit ``with gil`` block.
* C++ functions can now be declared as potentially raising both C++ and Python
exceptions, so that Cython can handle both correctly.
(Github issue 2615)
* ``cython.inline()`` supports a direct ``language_level`` keyword argument that
was previously only available via a directive.
* A new language level name ``3str`` was added that mostly corresponds to language
level 3, but keeps unprefixed string literals as type 'str' in both Py2 and Py3,
and the builtin 'str' type unchanged. This will become the default in the next
Cython release and is meant to help user code a) transition more easily to this
new default and b) migrate to Python 3 source code semantics without making support
for Python 2.x difficult.
* In CPython 3.6 and later, looking up globals in the module dict is almost
as fast as looking up C globals.
(Github issue 2313)
* For a Python subclass of an extension type, repeated method calls to non-overridden
cpdef methods can avoid the attribute lookup in Py3.6+, which makes them 4x faster.
(Github issue 2313)
* (In-)equality comparisons of objects to integer literals are faster.
(Github issue 2188)
* Some internal and 1-argument method calls are faster.
* Modules that cimport many external extension types from other Cython modules
execute less import requests during module initialisation.
* Constant tuples and slices are deduplicated and only created once per module.
(Github issue 2292)
* The coverage plugin considers more C file extensions such as ``.cc`` and ``.cxx``.
(Github issue 2266)
* The ``cythonize`` command accepts compile time variable values (as set by ``DEF``)
through the new ``-E`` option.
Patch by Jerome Kieffer. (Github issue 2315)
* ``pyximport`` can import from namespace packages.
Patch by Prakhar Goel. (Github issue 2294)
* Some missing numpy and CPython C-API declarations were added.
Patch by John Kirkham. (Github issues 2523, 2520, 2537)
* Declarations for the ``pylifecycle`` C-API functions were added in a new .pxd file
``cpython.pylifecycle``.
* The Pythran support was updated to work with the latest Pythran 0.8.7.
Original patch by Adrien Guinet. (Github issue 2600)
* ``%a`` is included in the string formatting types that are optimised into f-strings.
In this case, it is also automatically mapped to ``%r`` in Python 2.x.
* New C macro ``CYTHON_HEX_VERSION`` to access Cython's version in the same style as
``PY_VERSION_HEX``.
* Constants in ``libc.math`` are now declared as ``const`` to simplify their handling.
* An additional ``check_size`` clause was added to the ``ctypedef class`` name
specification to allow suppressing warnings when importing modules with
backwards-compatible ``PyTypeObject`` size changes.
Patch by Matti Picus. (Github issue 2627)
Bugs fixed
----------
* The exception handling in generators and coroutines under CPython 3.7 was adapted
to the newly introduced exception stack. Users of Cython 0.28 who want to support
Python 3.7 are encouraged to upgrade to 0.29 to avoid potentially incorrect error
reporting and tracebacks. (Github issue 1958)
* Crash when importing a module under Stackless Python that was built for CPython.
Patch by Anselm Kruis. (Github issue 2534)
* 2-value slicing of typed sequences failed if the start or stop index was None.
Patch by Christian Gibson. (Github issue 2508)
* Multiplied string literals lost their factor when they are part of another
constant expression (e.g. 'x' * 10 + 'y' => 'xy').
* String formatting with the '%' operator didn't call the special ``__rmod__()``
method if the right side is a string subclass that implements it.
(Python issue 28598)
* The directive ``language_level=3`` did not apply to the first token in the
source file. (Github issue 2230)
* Overriding cpdef methods did not work in Python subclasses with slots.
Note that this can have a performance impact on calls from Cython code.
(Github issue 1771)
* Fix declarations of builtin or C types using strings in pure python mode.
(Github issue 2046)
* Generator expressions and lambdas failed to compile in ``cfunc`` functions.
(Github issue 459)
* Global names with ``const`` types were not excluded from star-import assignments
which could lead to invalid C code.
(Github issue 2621)
* Several internal function signatures were fixed that lead to warnings in gcc-8.
(Github issue 2363)
* The numpy helper functions ``set_array_base()`` and ``get_array_base()``
were adapted to the current numpy C-API recommendations.
Patch by Matti Picus. (Github issue 2528)
* Some NumPy related code was updated to avoid deprecated API usage.
Original patch by jbrockmendel. (Github issue 2559)
* Several C++ STL declarations were extended and corrected.
Patch by Valentin Valls. (Github issue 2207)
* C lines of the module init function were unconditionally not reported in
exception stack traces.
Patch by Jeroen Demeyer. (Github issue 2492)
* When PEP-489 support is enabled, reloading the module overwrote any static
module state. It now raises an exception instead, given that reloading is
not actually supported.
* Object-returning, C++ exception throwing functions were not checking that
the return value was non-null.
Original patch by Matt Wozniski (Github Issue 2603)
* The source file encoding detection could get confused if the
``c_string_encoding`` directive appeared within the first two lines.
(Github issue 2632)
* Cython generated modules no longer emit a warning during import when the
size of the NumPy array type is larger than what was found at compile time.
Instead, this is assumed to be a backwards compatible change on NumPy side.
Other changes
-------------
* Cython now emits a warning when no ``language_level`` (2, 3 or '3str') is set
explicitly, neither as a ``cythonize()`` option nor as a compiler directive.
This is meant to prepare the transition of the default language level from
currently Py2 to Py3, since that is what most new users will expect these days.
The future default will, however, not enforce unicode literals, because this
has proven a major obstacle in the support for both Python 2.x and 3.x. The
next major release is intended to make this change, so that it will parse all
code that does not request a specific language level as Python 3 code, but with
``str`` literals. The language level 2 will continue to be supported for an
indefinite time.
* The documentation was restructured, cleaned up and examples are now tested.
The NumPy tutorial was also rewritten to simplify the running example.
Contributed by Gabriel de Marmiesse. (Github issue 2245)
* Cython compiles less of its own modules at build time to reduce the installed
package size to about half of its previous size. This makes the compiler
slightly slower, by about 5-7%.