CHANGES.rst



Cython Changelog

3.0.0 alpha 6 (2020-0?-??)

Features added

Special methods for binary operators now follow Python semantics.
Rather than e.g. a single __add__ method for cdef classes, where
"self" can be either the first or second argument, one can now define
both __add__ and __radd__ as for standard Python classes .
This behavior can be disabled with the c_api_binop_methods directive
to return to the previous semantics in Cython code.
(Github issue #2056)
No/single argument functions now accept keyword arguments by default in order
to comply with Python semantics.  The marginally faster calling conventions
METH_NOARGS and METH_O that reject keyword arguments are still available
with the directive @cython.always_allow_keywords(False).
(Github issue #3090)
The @returns() decorator propagates exceptions by default for suitable C
return types when no @exceptval() is defined.
(Github issue #3664)
A low-level inline function total_seconds(timedelta) was added to
cpython.datetime to bypass the Python method call.  Note that this function
is not guaranteed to give exactly the same results for very large time intervals.
Patch by Brock Mendel.  (Github issue #3616)
Type inference now understands that a, *b = x assigns a list to b.


Bugs fixed

The C++ typeid() function was allowed in C mode.
Patch by Celelibi.  (Github issue #3637)
Includes all bug-fixes from the 0.29.20 release.


Other changes

The numpy declarations were updated.
Patch by Brock Mendel.  (Github issue #3630)
The names of Cython's internal types (functions, generator, coroutine, etc.)
are now qualified with the module name of the internal Cython module that is
used for sharing them across Cython implemented modules, for example
_cython_3_0a5.coroutine.  This was done to avoid making them look like
homeless builtins, to help with debugging, and in order to avoid a CPython
warning according to https://bugs.python.org/issue20204


3.0.0 alpha 5 (2020-05-19)

Features added


.pxd files can now be versioned by adding an extension like ".cython-30.pxd"
to prevent older Cython versions (than 3.0 in this case) from picking them up.
(Github issue #3577)
Several macros/functions declared in the NumPy API are now usable without
holding the GIL.

libc.math was extended to include all C99 function declarations.
Patch by Dean Scarff.  (Github issue #3570)


Bugs fixed

Several issues with arithmetic overflow handling were resolved, including
undefined behaviour in C.
Patch by Sam Sneddon.  (Github issue #3588)
The improved GIL handling in nogil functions introduced in 3.0a3
could fail to acquire the GIL in some cases on function exit.
(Github issue #3590 etc.)
A reference leak when processing keyword arguments in Py2 was resolved,
that appeared in 3.0a1.
(Github issue #3578)
The outdated getbuffer/releasebuffer implementations in the NumPy
declarations were removed so that buffers declared as ndarray
now use the normal implementation in NumPy.
Includes all bug-fixes from the 0.29.18 release.


3.0.0 alpha 4 (2020-05-05)

Features added

The print statement (not the print() function) is allowed in
nogil code without an explicit with gil section.
The assert statement is allowed in nogil sections.  Here, the GIL is
only acquired if the AssertionError is really raised, which means that the
evaluation of the asserted condition only allows C expressions.
Cython generates C compiler branch hints for unlikely user defined if-clauses
in more cases, when they end up raising exceptions unconditionally. This now
includes exceptions being raised in nogil/with gil sections.
Some internal memoryview functions were tuned to reduce object overhead.


Bugs fixed

Exception position reporting could run into race conditions on threaded code.
It now uses function-local variables again.
Error handling early in the module init code could lead to a crash.
Error handling in cython.array creation was improved to avoid calling
C-API functions with an error held.
Complex buffer item types of structs of arrays could fail to validate.
Patch by Leo and smutch.  (Github issue #1407)
When importing the old Cython build_ext integration with distutils, the
additional command line arguments leaked into the regular command.
Patch by Kamekameha.  (Github issue #2209)
The improved GIL handling in nogil functions introduced in 3.0a3
could generate invalid C code.
(Github issue #3558)

PyEval_InitThreads() is no longer used in Py3.7+ where it is a no-op.
Parallel builds of Cython itself (setup.py build_ext -j N) failed on Windows.


Other changes

The C property feature has been rewritten and now requires C property methods
to be declared inline.


3.0.0 alpha 3 (2020-04-27)

Features added


nogil functions now avoid acquiring the GIL on function exit if possible
even if they contain with gil blocks.
(Github issue #3554)
Python private name mangling now falls back to unmangled names for non-Python
globals, since double-underscore names are not uncommon in C.  Unmangled Python
names are also still found as a legacy fallback but produce a warning.
Patch by David Woods.  (Github issue #3548)


Bugs fixed

Includes all bug-fixes from the 0.29.17 release.


3.0.0 alpha 2 (2020-04-23)

Features added


std::move() is now used in C++ mode for internal temp variables to
make them work without copying values.
Patch by David Woods.  (Github issues #3253, 1612)

__class_getitem__ is supported for types on item access (PEP-560).
Patch by msg555.  (Github issue #2753)
The simplified Py3.6 customisation of class creation is implemented (PEP-487).
(Github issue #2781)
Conditional blocks in Python code that depend on cython.compiled are
eliminated at an earlier stage, which gives more freedom in writing
replacement Python code.
Patch by David Woods.  (Github issue #3507)

numpy.import_array() is automatically called if numpy has been cimported
and it has not been called in the module code.  This is intended as a hidden
fail-safe so user code should continue to call numpy.import_array.
Patch by David Woods.  (Github issue #3524)
The Cython AST code serialiser class CodeWriter in Cython.CodeWriter
supports more syntax nodes.
The fastcall/vectorcall protocols are used for several internal Python calls.
(Github issue #3540)


Bugs fixed

With language_level=3/3str, Python classes without explicit base class
are now new-style (type) classes also in Py2.  Previously, they were created
as old-style (non-type) classes.
(Github issue #3530)
C++ typeid() failed for fused types.
Patch by David Woods.  (Github issue #3203)

__arg argument names in methods were not mangled with the class name.
Patch by David Woods.  (Github issue #1382)
Creating an empty unicode slice with large bounds could crash.
Patch by Sam Sneddon.  (Github issue #3531)
Decoding an empty bytes/char* slice with large bounds could crash.
Patch by Sam Sneddon.  (Github issue #3534)
Temporary buffer indexing variables were not released and could show up in
C compiler warnings, e.g. in generators.
Patch by David Woods.  (Github issues #3430, #3522)
Several C compiler warnings were fixed.


3.0.0 alpha 1 (2020-04-12)

Features added

Cython functions now use the PEP-590 vectorcall protocol in Py3.7+.
Patch by Jeroen Demeyer.  (Github issue #2263)
Unicode identifiers are supported in Cython code (PEP 3131).
Patch by David Woods.  (Github issue #2601)
Unicode module names and imports are supported.
Patch by David Woods.  (Github issue #3119)
Annotations are no longer parsed, keeping them as strings following PEP-563.
Patch by David Woods.  (Github issue #3285)
Preliminary support for the CPython's Py_LIMITED_API (stable ABI) is
available by setting the  CYTHON_LIMITED_API C macro.  Note that the
support is currently in an early stage and many features do not yet work.
Patches by Eddie Elizondo and David Woods.  (Github issues #3223, #3311, #3501)
The dispatch to fused functions is now linear in the number of arguments,
which makes it much faster, often 2x or more, and several times faster for
larger fused types with many specialisations.
Patch by will-ca.  (Github issue #1385)

with gil/nogil statements can be conditional based on compile-time
constants, e.g. fused type checks.
Patch by Noam Hershtig.  (Github issue #2579)

const can be used together with fused types.
Patch by Thomas Vincent.  (Github issue #1772)
Reimports of already imported modules are substantially faster.
(Github issue #2854)
Positional-only arguments are supported in Python functions.
Patch by Josh Tobin.  (Github issue #2915)
The volatile C modifier is supported in Cython code.
Patch by Jeroen Demeyer.  (Github issue #1667)

@cython.trashcan(True) can be used on an extension type to enable the
CPython trashcan. This allows deallocating deeply recursive objects without
overflowing the stack.  Patch by Jeroen Demeyer.  (Github issue #2842)
Inlined properties can be defined for external extension types.
Patch by Matti Picus.  (Github issue #2640)
The str() builtin now calls PyObject_Str() instead of going
through a Python call.
Patch by William Ayd.  (Github issue #3279)
String concatenation can now happen in place if possible, by extending the
existing string rather than always creating a new one.
Patch by David Woods.  (Github issue #3453)
Multiplication of Python numbers with small constant integers is faster.
(Github issue #2808)
Some list copying is avoided internally when a new list needs to be created
but we already have a fresh one.
(Github issue #3494)
Extension types that do not need their own tp_new implementation (because
they have no object attributes etc.) directly inherit the implementation of
their parent type if possible.
(Github issue #1555)
The attributes gen.gi_frame and coro.cr_frame of Cython compiled
generators and coroutines now return an actual frame object for introspection.
(Github issue #2306)
Several declarations in cpython.*, libc.* and libcpp.* were added.
Patches by Jeroen Demeyer, Matthew Edwards, Chris Gyurgyik, Jerome Kieffer
and Zackery Spytz.
(Github issues #3468, #3332, #3202, #3188, #3179, #2891, #2826, #2713)
Deprecated NumPy API usages were removed from numpy.pxd.
Patch by Matti Picus.  (Github issue #3365)

cython.inline() now sets the NPY_NO_DEPRECATED_API=NPY_1_7_API_VERSION
C macro automatically when numpy is imported in the code, to avoid C compiler
warnings about deprecated NumPy C-API usage.
The builtin abs() function can now be used on C numbers in nogil code.
Patch by Elliott Sales de Andrade.  (Github issue #2748)
PEP-479 (generator_stop) is now enabled by default with language level 3.
(Github issue #2580)
The cython.view.array type supports inheritance.
Patch by David Woods.  (Github issue #3413)
Code annotation accepts a new debugging argument --annotate-fullc that
will include the complete syntax highlighted C file in the HTML output.
(Github issue #2855)

--no-capture added to runtests.py to prevent stdout/stderr capturing
during srctree tests.
Patch by Matti Picus.  (Github issue #2701)

--no-docstrings option added to cythonize script.
Original patch by mo-han.  (Github issue #2889)

cygdb gives better error messages when it fails to initialise the
Python runtime support in gdb.
Patch by Volker Weissmann.  (Github issue #3489)
The Pythran shape attribute is supported.
Patch by Serge Guelton.  (Github issue #3307)


Bugs fixed

The unicode methods .upper(), .lower() and .title() were
incorrectly optimised for single character input values and only returned
the first character if multiple characters should have been returned.
They now use the original Python methods again.
Fused argument types were not correctly handled in type annotations and
cython.locals().
Patch by David Woods.  (Github issues #3391, #3142)
Diverging from the usual behaviour, len(memoryview), len(char*)
and len(Py_UNICODE*) returned an unsigned size_t value.  They now
return a signed Py_ssize_t, like other usages of len().
Nested dict literals in function call kwargs could incorrectly raise an
error about duplicate keyword arguments, which are allowed when passing
them from dict literals.
(Github issue #2963)
Item access (subscripting) with integer indices/keys always tried the
Sequence protocol before the Mapping protocol, which diverged from Python
semantics.  It now passes through the Mapping protocol first when supported.
(Github issue #1807)
Name lookups in class bodies no longer go through an attribute lookup.
Patch by Jeroen Demeyer.  (Github issue #3100)
Broadcast assignments to a multi-dimensional memory view slice could end
up in the wrong places when the underlying memory view is known to be
contiguous but the slice is not.
(Github issue #2941)
Pickling unbound methods of Python classes failed.
Patch by Pierre Glaser.  (Github issue #2972)
The Py_hash_t type failed to accept arbitrary "index" values.
(Github issue #2752)
The first function line number of functions with decorators pointed to the
signature line and not the first decorator line, as in Python.
Patch by Felix Kohlgrüber.  (Github issue #2536)
Constant integer expressions that used a negative exponent were evaluated
as integer 0 instead of the expected float value.
Patch by Kryštof Pilnáček.  (Github issue #2133)
The cython.declare() and cython.cast() functions could fail in pure mode.
Patch by Dmitry Shesterkin.  (Github issue #3244)

__doc__ was not available inside of the class body during class creation.
(Github issue #1635)
Setting language_level=2 in a file did not work if language_level=3
was enabled globally before.
Patch by Jeroen Demeyer.  (Github issue #2791)

__init__.pyx files were not always considered as package indicators.
(Github issue #2665)
Compiling package __init__ files could fail under Windows due to an
undefined export symbol.  (Github issue #2968)
A C compiler cast warning was resolved.
Patch by Michael Buesch.  (Github issue #2775)
Binding staticmethods of Cython functions were not behaving like Python methods.
Patch by Jeroen Demeyer.  (Github issue #3106, #3102)
Memoryviews failed to compile when the cache_builtins feature was disabled.
Patch by David Woods.  (Github issue #3406)


Other changes

The default language level was changed to 3str, i.e. Python 3 semantics,
but with str literals (also in Python 2.7).  This is a backwards incompatible
change from the previous default of Python 2 semantics.  The previous behaviour
is available through the directive language_level=2.
(Github issue #2565)
Cython no longer generates __qualname__ attributes for classes in Python
2.x since they are problematic there and not correctly maintained for subclasses.
Patch by Jeroen Demeyer.  (Github issue #2772)
Source file fingerprinting now uses SHA-1 instead of MD5 since the latter
tends to be slower and less widely supported these days.
(Github issue #2790)
The long deprecated include files python_*, stdio, stdlib and
stl in Cython/Includes/Deprecated/ were removed.  Use the libc.*
and cpython.* pxd modules instead.
Patch by Jeroen Demeyer.  (Github issue #2904)
The search order for include files was changed. Previously it was
include_directories, Cython/Includes, sys.path. Now it is
include_directories, sys.path, Cython/Includes. This was done to
allow third-party *.pxd files to override the ones in Cython.
Patch by Matti Picus.  (Github issue #2905)
The command line parser was rewritten and modernised using argparse.
Patch by Egor Dranischnikow.  (Github issue #2952, #3001)
Dotted filenames for qualified module names (pkg.mod.pyx) are deprecated.
Use the normal Python package directory layout instead.
(Github issue #2686)
Binary Linux wheels now follow the manylinux2010 standard.
Patch by Alexey Stepanov.  (Github issue #3355)
Support for Python 2.6 was removed.


0.29.21 (2020-0?-??)
Bugs fixed

The deprecated C-API function PyUnicode_FromUnicode() is no longer used.
Original patch by Inada Naoki.  (Github issue #3677)


0.29.20 (2020-06-10)
Bugs fixed

Nested try-except statements with multiple return statements could crash
due to incorrect deletion of the except as target variable.
(Github issue #3666)
The @classmethod decorator no longer rejects unknown input from other decorators.
Patch by David Woods.  (Github issue #3660)
Fused types could leak into unrelated usages.
Patch by David Woods.  (Github issue #3642)
Now uses Py_SET_SIZE() and Py_SET_REFCNT() in Py3.9+ to avoid low-level
write access to these object fields.
Patch by Victor Stinner.  (Github issue #3639)
The built-in abs() function could lead to undefined behaviour when used on
the negative-most value of a signed C integer type.
Patch by Serge Guelton.  (Github issue #1911)
Usages of sizeof() and typeid() on uninitialised variables no longer
produce a warning.
Patch by Celelibi.  (Github issue #3575)
The C++ typeid() function was allowed in C mode.
Patch by Celelibi.  (Github issue #3637)
The error position reported for errors found in f-strings was misleading.
(Github issue #3674)
The new c_api_binop_methods directive was added for forward compatibility, but can
only be set to True (the current default value).  It can be disabled in Cython 3.0.


0.29.19 (2020-05-20)
Bugs fixed

A typo in Windows specific code in 0.29.18 was fixed that broke "libc.math".
(Github issue #3622)
A platform specific test failure in 0.29.18 was fixed.
Patch by smutch.  (Github issue #3620)


0.29.18 (2020-05-18)
Bugs fixed

Exception position reporting could run into race conditions on threaded code.
It now uses function-local variables again.
Error handling early in the module init code could lead to a crash.
Error handling in cython.array creation was improved to avoid calling
C-API functions with an error held.
A memory corruption was fixed when garbage collection was triggered during calls
to PyType_Ready() of extension type subclasses.
(Github issue #3603)
Memory view slicing generated unused error handling code which could negatively
impact the C compiler optimisations for parallel OpenMP code etc.  Also, it is
now helped by static branch hints.
(Github issue #2987)
Cython's built-in OpenMP functions were not translated inside of call arguments.
Original patch by Celelibi and David Woods.  (Github issue #3594)
Complex buffer item types of structs of arrays could fail to validate.
Patch by Leo and smutch.  (Github issue #1407)
Decorators were not allowed on nested async def functions.
(Github issue #1462)
C-tuples could use invalid C struct casting.
Patch by MegaIng.  (Github issue #3038)
Optimised %d string formatting into f-strings failed on float values.
(Github issue #3092)
Optimised aligned string formatting (%05s, %-5s) failed.
(Github issue #3476)
When importing the old Cython build_ext integration with distutils, the
additional command line arguments leaked into the regular command.
Patch by Kamekameha.  (Github issue #2209)
When using the CYTHON_NO_PYINIT_EXPORT option in C++, the module init function
was not declared as extern "C".
(Github issue #3414)
Three missing timedelta access macros were added in cpython.datetime.
The signature of the NumPy C-API function PyArray_SearchSorted() was fixed.
Patch by Brock Mendel.  (Github issue #3606)


0.29.17 (2020-04-26)

Features added


std::move() is now available from libcpp.utility.
Patch by Omer Ozarslan.  (Github issue #2169)
The @cython.binding decorator is available in Python code.
(Github issue #3505)


Bugs fixed

Creating an empty unicode slice with large bounds could crash.
Patch by Sam Sneddon.  (Github issue #3531)
Decoding an empty bytes/char* slice with large bounds could crash.
Patch by Sam Sneddon.  (Github issue #3534)
Re-importing a Cython extension no longer raises the error
"__reduce_cython__ not found".
(Github issue #3545)
Unused C-tuples could generate incorrect code in 0.29.16.
Patch by Kirk Meyer.  (Github issue #3543)
Creating a fused function attached it to the garbage collector before it
was fully initialised, thus risking crashes in rare failure cases.
Original patch by achernomorov.  (Github issue #3215)
Temporary buffer indexing variables were not released and could show up in
C compiler warnings, e.g. in generators.
Patch by David Woods.  (Github issues #3430, #3522)
The compilation cache in cython.inline("…") failed to take the language
level into account.
Patch by will-ca.  (Github issue #3419)
The deprecated PyUnicode_GET_SIZE() function is no longer used in Py3.


0.29.16 (2020-03-24)
Bugs fixed

Temporary internal variables in nested prange loops could leak into other
threads.  Patch by Frank Schlimbach.  (Github issue #3348)
Default arguments on fused functions could crash.
Patch by David Woods.  (Github issue #3370)
C-tuples declared in .pxd files could generate incomplete C code.
Patch by Kirk Meyer.  (Github issue #1427)
Fused functions were not always detected and optimised as Cython
implemented functions.
Patch by David Woods.  (Github issue #3384)
Valid Python object concatenation of (iterable) strings to non-strings
could fail with an exception.
Patch by David Woods.  (Github issue #3433)
Using C functions as temporary values lead to invalid C code.
Original patch by David Woods.  (Github issue #3418)
Fix an unhandled C++ exception in comparisons.
Patch by David Woods.  (Github issue #3361)
Fix deprecated import of "imp" module.
Patch by Matti Picus.  (Github issue #3350)
Fix compatibility with Pythran 0.9.6 and later.
Patch by Serge Guelton.  (Github issue #3308)
The _Py_PyAtExit() function in cpython.pylifecycle was misdeclared.
Patch by Zackery Spytz.  (Github issue #3382)
Several missing declarations in cpython.* were added.
Patches by Zackery Spytz.  (Github issue #3452, #3421, #3411, #3402)
A declaration for libc.math.fpclassify() was added.
Patch by Zackery Spytz.  (Github issue #2514)
Avoid "undeclared" warning about automatically generated pickle methods.
Patch by David Woods.  (Github issue #3353)
Avoid C compiler warning about unreachable code in prange().
Some C compiler warnings in PyPy were resolved.
Patch by Matti Picus.  (Github issue #3437)


0.29.15 (2020-02-06)
Bugs fixed

Crash when returning a temporary Python object from an async-def function.
(Github issue #3337)
Crash when using **kwargs in generators.
Patch by David Woods.  (Github issue #3265)
Double reference free in __class__ cell handling for super() calls.
(Github issue #3246)
Compile error when using *args as Python class bases.
(Github issue #3338)
Import failure in IPython 7.11.
(Github issue #3297)
Fixed C name collision in the auto-pickle code.
Patch by ThePrez.  (Github issue #3238)
Deprecated import failed in Python 3.9.
(Github issue #3266)


0.29.14 (2019-11-01)

Bugs fixed

The generated code failed to initialise the tp_print slot in CPython 3.8.
Patches by Pablo Galindo and Orivej Desh.  (Github issues #3171, #3201)

? for bool was missing from the supported NumPy dtypes.
Patch by Max Klein.  (Github issue #2675)

await was not allowed inside of f-strings.
Patch by Dmitro Getz.  (Github issue #2877)
Coverage analysis failed for projects where the code resides in separate
source sub-directories.
Patch by Antonio Valentino.  (Github issue #1985)
An incorrect compiler warning was fixed in automatic C++ string conversions.
Patch by Gerion Entrup.  (Github issue #3108)
Error reports in the Jupyter notebook showed unhelpful stack traces.
Patch by Matthew Edwards (Github issue #3196).

Python.h is now also included explicitly from public header files.
(Github issue #3133).
Distutils builds with --parallel did not work when using Cython's
deprecated build_ext command.
Patch by Alphadelta14 (Github issue #3187).


Other changes

The PyMemoryView_*() C-API is available in cpython.memoryview.
Patch by Nathan Manville.  (Github issue #2541)


0.29.13 (2019-07-26)

Bugs fixed

A reference leak for None was fixed when converting a memoryview
to a Python object.  (Github issue #3023)
The declaration of PyGILState_STATE in cpython.pystate was unusable.
Patch by Kirill Smelkov.  (Github issue #2997)


Other changes

The declarations in posix.mman were extended.
Patches by Kirill Smelkov.  (Github issues #2893, #2894, #3012)


0.29.12 (2019-07-07)
Bugs fixed

Fix compile error in CPython 3.8b2 regarding the PyCode_New() signature.
(Github issue #3031)
Fix a C compiler warning about a missing int downcast.
(Github issue #3028)
Fix reported error positions of undefined builtins and constants.
Patch by Orivej Desh.  (Github issue #3030)
A 32 bit issue in the Pythran support was resolved.
Patch by Serge Guelton.  (Github issue #3032)


0.29.11 (2019-06-30)
Bugs fixed

Fix compile error in CPython 3.8b2 regarding the PyCode_New() signature.
Patch by Nick Coghlan. (Github issue #3009)
Invalid C code generated for lambda functions in cdef methods.
Patch by Josh Tobin.  (Github issue #2967)
Support slice handling in newer Pythran versions.
Patch by Serge Guelton.  (Github issue #2989)
A reference leak in power-of-2 calculation was fixed.
Patch by Sebastian Berg.  (Github issue #3022)
The search order for include files was changed. Previously it was
include_directories, Cython/Includes, sys.path. Now it is
include_directories, sys.path, Cython/Includes. This was done to
allow third-party *.pxd files to override the ones in Cython.
Original patch by Matti Picus.  (Github issue #2905)
Setting language_level=2 in a file did not work if language_level=3
was enabled globally before.
Patch by Jeroen Demeyer.  (Github issue #2791)


0.29.10 (2019-06-02)
Bugs fixed

Fix compile errors in CPython 3.8b1 due to the new "tp_vectorcall" slots.
(Github issue #2976)


0.29.9 (2019-05-29)
Bugs fixed

Fix a crash regression in 0.29.8 when creating code objects fails.
Remove an incorrect cast when using true-division in C++ operations.
(Github issue #1950)


0.29.8 (2019-05-28)
Bugs fixed

C compile errors with CPython 3.8 were resolved.
Patch by Marcel Plch.  (Github issue #2938)
Python tuple constants that compare equal but have different item
types could incorrectly be merged into a single constant.
(Github issue #2919)
Non-ASCII characters in unprefixed strings could crash the compiler when
used with language level 3str.
Starred expressions in %-formatting tuples could fail to compile for
unicode strings.  (Github issue #2939)
Passing Python class references through cython.inline() was broken.
(Github issue #2936)


0.29.7 (2019-04-14)
Bugs fixed

Crash when the shared Cython config module gets unloaded and another Cython
module reports an exceptions.  Cython now makes sure it keeps an owned reference
to the module.
(Github issue #2885)
Resolved a C89 compilation problem when enabling the fast-gil sharing feature.
Coverage reporting did not include the signature line of cdef functions.
(Github issue #1461)
Casting a GIL-requiring function into a nogil function now issues a warning.
(Github issue #2879)
Generators and coroutines were missing their return type annotation.
(Github issue #2884)


0.29.6 (2019-02-27)
Bugs fixed

Fix a crash when accessing the __kwdefaults__ special attribute of
fused functions.  (Github issue #1470)
Fix the parsing of buffer format strings that contain numeric sizes, which
could lead to incorrect input rejections.  (Github issue #2845)
Avoid a C #pragma in old gcc versions that was only added in GCC 4.6.
Patch by Michael Anselmi.  (Github issue #2838)
Auto-encoding of Unicode strings to UTF-8 C/C++ strings failed in Python 3,
even though the default encoding there is UTF-8.
(Github issue #2819)


0.29.5 (2019-02-09)
Bugs fixed

Crash when defining a Python subclass of an extension type and repeatedly calling
a cpdef method on it.  (Github issue #2823)
Compiler crash when prange() loops appear inside of with-statements.
(Github issue #2780)
Some C compiler warnings were resolved.
Patches by Christoph Gohlke.  (Github issues #2815, #2816, #2817, #2822)
Python conversion of C++ enums failed in 0.29.
Patch by Orivej Desh.  (Github issue #2767)


0.29.4 (2019-02-01)
Bugs fixed

Division of numeric constants by a runtime value of 0 could fail to raise a
ZeroDivisionError.  (Github issue #2820)


0.29.3 (2019-01-19)
Bugs fixed

Some C code for memoryviews was generated in a non-deterministic order.
Patch by Martijn van Steenbergen.  (Github issue #2779)
C89 compatibility was accidentally lost since 0.28.
Patches by gastineau and true-pasky.  (Github issues #2778, #2801)
A C compiler cast warning was resolved.
Patch by Michael Buesch.  (Github issue #2774)
An compilation failure with complex numbers under MSVC++ was resolved.
(Github issue #2797)
Coverage reporting could fail when modules were moved around after the build.
Patch by Wenjun Si.  (Github issue #2776)


0.29.2 (2018-12-14)
Bugs fixed

The code generated for deduplicated constants leaked some references.
(Github issue #2750)
The declaration of sigismember() in libc.signal was corrected.
(Github issue #2756)
Crashes in compiler and test runner were fixed.
(Github issue #2736, #2755)
A C compiler warning about an invalid safety check was resolved.
(Github issue #2731)


0.29.1 (2018-11-24)
Bugs fixed

Extensions compiled with MinGW-64 under Windows could misinterpret integer
objects larger than 15 bit and return incorrect results.
(Github issue #2670)
Cython no longer requires the source to be writable when copying its data
into a memory view slice.
Patch by Andrey Paramonov.  (Github issue #2644)
Line tracing of try-statements generated invalid C code.
(Github issue #2274)
When using the warn.undeclared directive, Cython's own code generated
warnings that are now fixed.
Patch by Nicolas Pauss.  (Github issue #2685)
Cython's memoryviews no longer require strides for setting the shape field
but only the PyBUF_ND flag to be set.
Patch by John Kirkham.  (Github issue #2716)
Some C compiler warnings about unused memoryview code were fixed.
Patch by Ho Cheuk Ting.  (Github issue #2588)
A C compiler warning about implicit signed/unsigned conversion was fixed.
(Github issue #2729)
Assignments to C++ references returned by operator[] could fail to compile.
(Github issue #2671)
The power operator and the support for NumPy math functions were fixed
in Pythran expressions.
Patch by Serge Guelton.  (Github issues #2702, #2709)
Signatures with memory view arguments now show the expected type
when embedded in docstrings.
Patch by Matthew Chan and Benjamin Weigel.  (Github issue #2634)
Some from ... cimport ... constructs were not correctly considered
when searching modified dependencies in cythonize() to decide
whether to recompile a module.
Patch by Kryštof Pilnáček.  (Github issue #2638)
A struct field type in the cpython.array declarations was corrected.
Patch by John Kirkham.  (Github issue #2712)


0.29 (2018-10-14)

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%.


0.28.6 (2018-11-01)
Bugs fixed

Extensions compiled with MinGW-64 under Windows could misinterpret integer
objects larger than 15 bit and return incorrect results.
(Github issue #2670)
Multiplied string literals lost their factor when they are part of another
constant expression (e.g. 'x' * 10 + 'y' => 'xy').


0.28.5 (2018-08-03)
Bugs fixed

The discouraged usage of GCC's attribute optimize("Os") was replaced by the
similar attribute cold to reduce the code impact of the module init functions.
(Github issue #2494)
A reference leak in Py2.x was fixed when comparing str to unicode for equality.


0.28.4 (2018-07-08)
Bugs fixed

Reallowing tp_clear() in a subtype of an @no_gc_clear extension type
generated an invalid C function call to the (non-existent) base type implementation.
(Github issue #2309)
Exception catching based on a non-literal (runtime) tuple could fail to match the
exception.  (Github issue #2425)
Compile fix for CPython 3.7.0a2.  (Github issue #2477)


0.28.3 (2018-05-27)
Bugs fixed

Set iteration was broken in non-CPython since 0.28.

UnicodeEncodeError in Py2 when %s formatting is optimised for
unicode strings.  (Github issue #2276)
Work around a crash bug in g++ 4.4.x by disabling the size reduction setting
of the module init function in this version.  (Github issue #2235)
Crash when exceptions occur early during module initialisation.
(Github issue #2199)


0.28.2 (2018-04-13)

Features added


abs() is faster for Python long objects.
The C++11 methods front() and end() were added to the declaration of
libcpp.string.  Patch by Alex Huszagh.  (Github issue #2123)
The C++11 methods reserve() and bucket_count() are declared for
libcpp.unordered_map.  Patch by Valentin Valls.  (Github issue #2168)


Bugs fixed

The copy of a read-only memoryview was considered read-only as well, whereas
a common reason to copy a read-only view is to make it writable.  The result
of the copying is now a writable buffer by default.
(Github issue #2134)
The switch statement generation failed to apply recursively to the body of
converted if-statements.

NULL was sometimes rejected as exception return value when the returned
type is a fused pointer type.
Patch by Callie LeFave.  (Github issue #2177)
Fixed compatibility with PyPy 5.11.
Patch by Matti Picus.  (Github issue #2165)


Other changes

The NumPy tutorial was rewritten to use memoryviews instead of the older
buffer declaration syntax.
Contributed by Gabriel de Marmiesse.  (Github issue #2162)


0.28.1 (2018-03-18)
Bugs fixed


PyFrozenSet_New() was accidentally used in PyPy where it is missing
from the C-API.
Assignment between some C++ templated types were incorrectly rejected
when the templates mix const with ctypedef.
(Github issue #2148)
Undeclared C++ no-args constructors in subclasses could make the compilation
fail if the base class constructor was declared without nogil.
(Github issue #2157)
Bytes %-formatting inferred basestring (bytes or unicode) as result type
in some cases where bytes would have been safe to infer.
(Github issue #2153)

None was accidentally disallowed as typed return value of dict.pop().
(Github issue #2152)


0.28 (2018-03-13)

Features added

Cdef classes can now multiply inherit from ordinary Python classes.
(The primary base must still be a c class, possibly object, and
the other bases must not be cdef classes.)
Type inference is now supported for Pythran compiled NumPy expressions.
Patch by Nils Braun.  (Github issue #1954)
The const modifier can be applied to memoryview declarations to allow
read-only buffers as input.  (Github issues #1605, #1869)
C code in the docstring of a cdef extern block is copied verbatimly
into the generated file.
Patch by Jeroen Demeyer.  (Github issue #1915)
When compiling with gcc, the module init function is now tuned for small
code size instead of whatever compile flags were provided externally.
Cython now also disables some code intensive optimisations in that function
to further reduce the code size.  (Github issue #2102)
Decorating an async coroutine with @cython.iterable_coroutine changes its
type at compile time to make it iterable.  While this is not strictly in line
with PEP-492, it improves the interoperability with old-style coroutines that
use yield from instead of await.
The IPython magic has preliminary support for JupyterLab.
(Github issue #1775)
The new TSS C-API in CPython 3.7 is supported and has been backported.
Patch by Naotoshi Seo.  (Github issue #1932)
Cython knows the new Py_tss_t type defined in PEP-539 and automatically
initialises variables declared with that type to Py_tss_NEEDS_INIT,
a value which cannot be used outside of static assignments.
The set methods .remove() and .discard() are optimised.
Patch by Antoine Pitrou.  (Github issue #2042)

dict.pop() is optimised.
Original patch by Antoine Pitrou.  (Github issue #2047)
Iteration over sets and frozensets is optimised.
(Github issue #2048)
Safe integer loops (< range(2^30)) are automatically optimised into C loops.

alist.extend([a,b,c]) is optimised into sequential list.append() calls
for short literal sequences.
Calls to builtin methods that are not specifically optimised into C-API calls
now use a cache that avoids repeated lookups of the underlying C function.
(Github issue #2054)
Single argument function calls can avoid the argument tuple creation in some cases.
Some redundant extension type checks are avoided.
Formatting C enum values in f-strings is faster, as well as some other special cases.
String formatting with the '%' operator is optimised into f-strings in simple cases.
Subscripting (item access) is faster in some cases.
Some bytearray operations have been optimised similar to bytes.
Some PEP-484/526 container type declarations are now considered for
loop optimisations.
Indexing into memoryview slices with view[i][j] is now optimised into
view[i, j].
Python compatible cython.* types can now be mixed with type declarations
in Cython syntax.
Name lookups in the module and in classes are faster.
Python attribute lookups on extension types without instance dict are faster.
Some missing signals were added to libc/signal.pxd.
Patch by Jeroen Demeyer.  (Github issue #1914)
The warning about repeated extern declarations is now visible by default.
(Github issue #1874)
The exception handling of the function types used by CPython's type slot
functions was corrected to match the de-facto standard behaviour, so that
code that uses them directly benefits from automatic and correct exception
propagation.  Patch by Jeroen Demeyer.  (Github issue #1980)
Defining the macro CYTHON_NO_PYINIT_EXPORT will prevent the module init
function from being exported as symbol, e.g. when linking modules statically
in an embedding setup.  Patch by AraHaan.  (Github issue #1944)


Bugs fixed

If a module name is explicitly provided for an Extension() that is compiled
via cythonize(), it was previously ignored and replaced by the source file
name.  It can now be used to override the target module name, e.g. for compiling
prefixed accelerator modules from Python files.  (Github issue #2038)
The arguments of the num_threads parameter of parallel sections
were not sufficiently validated and could lead to invalid C code.
(Github issue #1957)
Catching exceptions with a non-trivial exception pattern could call into
CPython with a live exception set.  This triggered incorrect behaviour
and crashes, especially in CPython 3.7.
The signature of the special __richcmp__() method was corrected to recognise
the type of the first argument as self.  It was previously treated as plain
object, but CPython actually guarantees that it always has the correct type.
Note: this can change the semantics of user code that previously relied on
self being untyped.
Some Python 3 exceptions were not recognised as builtins when running Cython
under Python 2.
Some async helper functions were not defined in the generated C code when
compiling simple async code.  (Github issue #2075)
Line tracing did not include generators and coroutines.
(Github issue #1949)
C++ declarations for unordered_map were corrected.
Patch by Michael Schatzow.  (Github issue #1484)
Iterator declarations in C++ deque and vector were corrected.
Patch by Alex Huszagh.  (Github issue #1870)
The const modifiers in the C++ string declarations were corrected, together
with the coercion behaviour of string literals into C++ strings.
(Github issue #2132)
Some declaration types in libc.limits were corrected.
Patch by Jeroen Demeyer.  (Github issue #2016)

@cython.final was not accepted on Python classes with an @cython.cclass
decorator.  (Github issue #2040)
Cython no longer creates useless and incorrect PyInstanceMethod wrappers for
methods in Python 3.  Patch by Jeroen Demeyer.  (Github issue #2105)
The builtin bytearray type could not be used as base type of cdef classes.
(Github issue #2106)


Other changes

0.27.3 (2017-11-03)
Bugs fixed

String forward references to extension types like @cython.locals(x="ExtType")
failed to find the named type.  (Github issue #1962)
NumPy slicing generated incorrect results when compiled with Pythran.
Original patch by Serge Guelton (Github issue #1946).
Fix "undefined reference" linker error for generators on Windows in Py3.3-3.5.
(Github issue #1968)
Adapt to recent C-API change of PyThreadState in CPython 3.7.
Fix signature of PyWeakref_GetObject() API declaration.
Patch by Jeroen Demeyer (Github issue #1975).


0.27.2 (2017-10-22)
Bugs fixed

Comprehensions could incorrectly be optimised away when they appeared in boolean
test contexts.  (Github issue #1920)
The special methods __eq__, __lt__ etc. in extension types did not type
their first argument as the type of the class but object.  (Github issue #1935)
Crash on first lookup of "cline_in_traceback" option during exception handling.
(Github issue #1907)
Some nested module level comprehensions failed to compile.
(Github issue #1906)
Compiler crash on some complex type declarations in pure mode.
(Github issue #1908)

std::unordered_map.erase() was declared with an incorrect void return
type in libcpp.unordered_map.  (Github issue #1484)
Invalid use of C++ fallthrough attribute before C++11 and similar issue in clang.
(Github issue #1930)
Compiler crash on misnamed properties. (Github issue #1905)


0.27.1 (2017-10-01)

Features added

The Jupyter magic has a new debug option --verbose that shows details about
the distutils invocation.  Patch by Boris Filippov (Github issue #1881).


Bugs fixed

Py3 list comprehensions in class bodies resulted in invalid C code.
(Github issue #1889)
Modules built for later CPython 3.5.x versions failed to import in 3.5.0/3.5.1.
(Github issue #1880)
Deallocating fused types functions and methods kept their GC tracking enabled,
which could potentially lead to recursive deallocation attempts.
Crash when compiling in C++ mode with old setuptools versions.
(Github issue #1879)
C++ object arguments for the constructor of Cython implemented C++ are now
passed by reference and not by value to allow for non-copyable arguments, such
as unique_ptr.
API-exported C++ classes with Python object members failed to compile.
(Github issue #1866)
Some issues with the new relaxed exception value handling were resolved.
Python classes as annotation types could prevent compilation.
(Github issue #1887)
Cython annotation types in Python files could lead to import failures
with a "cython undefined" error.  Recognised types are now turned into strings.
Coverage analysis could fail to report on extension modules on some platforms.
Annotations could be parsed (and rejected) as types even with
annotation_typing=False.


Other changes

PEP 489 support has been disabled by default to counter incompatibilities with
import setups that try to reload or reinitialise modules.


0.27 (2017-09-23)

Features added

Extension module initialisation follows
PEP 489 in CPython 3.5+, which
resolves several differences with regard to normal Python modules.  This makes
the global names __file__ and __path__ correctly available to module
level code and improves the support for module-level relative imports.
(Github issues #1715, #1753, #1035)
Asynchronous generators (PEP 525)
and asynchronous comprehensions (PEP 530)
have been implemented.  Note that async generators require finalisation support
in order to allow for asynchronous operations during cleanup, which is only
available in CPython 3.6+.  All other functionality has been backported as usual.
Variable annotations are now parsed according to
PEP 526.  Cython types (e.g.
cython.int) are evaluated as C type declarations and everything else as Python
types.  This can be disabled with the directive annotation_typing=False.
Note that most complex PEP-484 style annotations are currently ignored.  This will
change in future releases. (Github issue #1850)
Extension types (also in pure Python mode) can implement the normal special methods
__eq__, __lt__ etc. for comparisons instead of the low-level __richcmp__
method.  (Github issue #690)
New decorator @cython.exceptval(x=None, check=False) that makes the signature
declarations except x, except? x and except * available to pure Python
code.  Original patch by Antonio Cuni.  (Github issue #1653)
Signature annotations are now included in the signature docstring generated by
the embedsignature directive.  Patch by Lisandro Dalcin (Github issue #1781).
The gdb support for Python code (libpython.py) was updated to the latest
version in CPython 3.7 (git rev 5fe59f8).
The compiler tries to find a usable exception return value for cdef functions
with except * if the returned type allows it.  Note that this feature is subject
to safety limitations, so it is still better to provide an explicit declaration.
C functions can be assigned to function pointers with a compatible exception
declaration, not only with exact matches.  A side-effect is that certain compatible
signature overrides are now allowed and some more mismatches of exception signatures
are now detected and rejected as errors that were not detected before.
The IPython/Jupyter magic integration has a new option %%cython --pgo for profile
guided optimisation. It compiles the cell with PGO settings for the C compiler,
executes it to generate a runtime profile, and then compiles it again using that
profile for C compiler optimisation.  Currently only tested with gcc.

len(memoryview) can be used in nogil sections to get the size of the
first dimension of a memory view (shape[0]). (Github issue #1733)
C++ classes can now contain (properly refcounted) Python objects.
NumPy dtype subarrays are now accessible through the C-API.
Patch by Gerald Dalley (Github issue #245).
Resolves several issues with PyPy and uses faster async slots in PyPy3.
Patch by Ronan Lamy (Github issues #1871, #1878).