CHANGES.rst



Cython Changelog

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

Features added

Added support for Python binary operator semantics.
One can now define, e.g. both __add__ and __radd__ for cdef classes
as for standard Python classes rather than a single __add__ method where
self can be either the first or second argument.  This behavior can be disabled
with the c_api_binop_methods directive.
(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)
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 0.29.19 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.


0.29.20 (2020-0?-??)
Bugs fixed

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)


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)