cython

Bugs fixed

• Fix a regression in 0.29.20 where __div__ failed to be found in extension types. (Github issue 3688)

• Fix a regression in 0.29.20 where a call inside of a finally clause could fail to compile. Patch by David Woods. (Github issue 3712)

• Zero-sized buffers could fail to validate as C/Fortran-contiguous. Patch by Clemens Hofreither. (Github issue 2093)

• exec() did not allow recent Python syntax features in Py3.8+ due to https://bugs.python.org/issue35975. (Github issue 3695)

• Binding staticmethods of Cython functions were not behaving like Python methods in Py3. Patch by Jeroen Demeyer and Michał Górny. (Github issue 3106)

• Pythran calls to NumPy methods no longer generate useless method lookup code.

• The PyUnicode_GET_LENGTH() macro was missing from the cpython.* declarations. Patch by Thomas Caswell. (Github issue 3692)

• The deprecated PyUnicode_*() C-API functions are no longer used, except for Unicode strings that contain lone surrogates. Unicode strings that contain non-BMP characters or surrogate pairs now generate different C code on 16-bit Python 2.x Unicode deployments (such as MS-Windows). Generating the C code on Python 3.x is recommended in this case. Original patches by Inada Naoki and Victor Stinner. (Github issues 3677, 3721, 3697)

• Some template parameters were missing from the C++ std::unordered_map declaration. Patch by will. (Github issue 3685)

• Several internal code generation issues regarding temporary variables were resolved. (Github issue 3708)

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.

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)

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)

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.

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)

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)

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)

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)

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)

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)

Bugs fixed

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

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)

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)

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)

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)

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)

Bugs fixed

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

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)

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)

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)

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%.

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').

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.

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)

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)

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)

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)

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

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).

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)

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.

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).

Bugs fixed

• Extension types that were cimported from other Cython modules could disagree about the order of fused cdef methods in their call table. This could lead to wrong methods being called and potentially also crashes. The fix required changes to the ordering of fused methods in the call table, which may break existing compiled modules that call fused cdef methods across module boundaries, if these methods were implemented in a different order than they were declared in the corresponding .pxd file. (Github issue 1873)

• The exception state handling in generators and coroutines could lead to exceptions in the caller being lost if an exception was raised and handled inside of the coroutine when yielding. (Github issue 1731)

• Loops over range(enum) were not converted into C for-loops. Note that it is still recommended to use an explicit cast to a C integer type in this case.

• Error positions of names (e.g. variables) were incorrectly reported after the name and not at the beginning of the name.

• Compile time DEF assignments were evaluated even when they occur inside of falsy IF blocks. (Github issue 1796)

• Disabling the line tracing from a trace function could fail. Original patch by Dmitry Trofimov. (Github issue 1769)

• Several issues with the Pythran integration were resolved.

• abs(signed int) now returns a signed rather than unsigned int. (Github issue 1837)

• Reading frame.f_locals of a Cython function (e.g. from a debugger or profiler could modify the module globals. (Github issue 1836)

• Buffer type mismatches in the NumPy buffer support could leak a reference to the buffer owner.

• Using the "is_f_contig" and "is_c_contig" memoryview methods together could leave one of them undeclared. (Github issue 1872)

• Compilation failed if the for-in-range loop target was not a variable but a more complex expression, e.g. an item assignment. (Github issue 1831)

• Compile time evaluations of (partially) constant f-strings could show incorrect results.

• Escape sequences in raw f-strings (fr'...') were resolved instead of passing them through as expected.

• Some ref-counting issues in buffer error handling have been resolved.

Other changes

• Type declarations in signature annotations are now parsed according to PEP 484 typing. Only Cython types (e.g. cython.int) and Python builtin types are currently considered as type declarations. Everything else is ignored, but this will change in a future Cython release. (Github issue 1672)

• The directive annotation_typing is now True by default, which enables parsing type declarations from annotations.

• This release no longer supports Python 3.2.

Features added

Bugs fixed

• cython.view.array was missing .__len__().

• Extension types with a .pxd override for their __releasebuffer__ slot (e.g. as provided by Cython for the Python array.array type) could leak a reference to the buffer owner on release, thus not freeing the memory. (Github issue 1638)

• Auto-decoding failed in 0.26 for strings inside of C++ containers. (Github issue 1790)

• Compile error when inheriting from C++ container types. (Github issue 1788)

• Invalid C code in generators (declaration after code). (Github issue 1801)

• Arithmetic operations on const integer variables could generate invalid code. (Github issue 1798)

• Local variables with names of special Python methods failed to compile inside of closures. (Github issue 1797)

• Problem with indirect Emacs buffers in cython-mode. Patch by Martin Albrecht (Github issue 1743).

• Extension types named result or PickleError generated invalid unpickling code. Patch by Jason Madden (Github issue 1786).

• Bazel integration failed to compile .py files. Patch by Guro Bokum (Github issue 1784).

• Some include directories and dependencies were referenced with their absolute paths in the generated files despite lying within the project directory.

• Failure to compile in Py3.7 due to a modified signature of _PyCFunctionFast()

Features added

• Pythran can be used as a backend for evaluating NumPy array expressions. Patch by Adrien Guinet (Github issue 1607).

• cdef classes now support pickling by default when possible. This can be disabled with the auto_pickle directive.

• Speed up comparisons of strings if their hash value is available. Patch by Claudio Freire (Github issue 1571).

• Support pyximport from zip files. Patch by Sergei Lebedev (Github issue 1485).

• IPython magic now respects the __all__ variable and ignores names with leading-underscore (like import * does). Patch by Syrtis Major (Github issue 1625).

• abs() is optimised for C complex numbers. Patch by David Woods (Github issue 1648).

• The display of C lines in Cython tracebacks can now be enabled at runtime via import cython_runtime; cython_runtime.cline_in_traceback=True. The default has been changed to False.

• The overhead of calling fused types generic functions was reduced.

• "cdef extern" include files are now also searched relative to the current file. Patch by Jeroen Demeyer (Github issue 1654).

• Optional optimization for re-acquiring the GIL, controlled by the fast_gil directive.

Bugs fixed

• Item lookup/assignment with a unicode character as index that is typed (explicitly or implicitly) as Py_UCS4 or Py_UNICODE used the integer value instead of the Unicode string value. Code that relied on the previous behaviour now triggers a warning that can be disabled by applying an explicit cast. (Github issue 1602)

• f-string processing was adapted to changes in PEP 498 and CPython 3.6.

• Invalid C code when decoding from UTF-16(LE/BE) byte strings. (Github issue 1696)

• Unicode escapes in 'ur' raw-unicode strings were not resolved in Py2 code. Original patch by Aaron Gallagher (Github issue 1594).

• File paths of code objects are now relative. Original patch by Jelmer Vernooij (Github issue 1565).

• Decorators of cdef class methods could be executed twice. Patch by Jeroen Demeyer (Github issue 1724).

• Dict iteration using the Py2 iter* methods failed in PyPy3. Patch by Armin Rigo (Github issue 1631).

• Several warnings in the generated code are now suppressed.

Other changes

• The unraisable_tracebacks option now defaults to True.

• Coercion of C++ containers to Python is no longer automatic on attribute access (Github issue 1521).

• Access to Python attributes of cimported modules without the corresponding import is now a compile-time (rather than runtime) error.

• Do not use special dll linkage for "cdef public" functions. Patch by Jeroen Demeyer (Github issue 1687).

• cdef/cpdef methods must match their declarations. See Github issue 1732. This is now a warning and will be an error in future releases.

Bugs fixed

• Fixes several issues with C++ template deduction.

• Fixes a issue with bound method type inference (Github issue 551).

• Fixes a bug with cascaded tuple assignment (Github issue 1523).

• Fixed or silenced many Clang warnings.

• Fixes bug with powers of pure real complex numbers (Github issue 1538).

Bugs fixed

• Fixes a bug with isinstance(o, Exception) (Github issue 1496).

• Fixes bug with cython.view.array missing utility code in some cases (Github issue 1502).

Other changes

• The distutils extension Cython.Distutils.build_ext has been reverted, temporarily, to be old_build_ext to give projects time to migrate. The new build_ext is available as new_build_ext.

Features added

• def/cpdef methods of cdef classes benefit from Cython's internal function implementation, which enables introspection and line profiling for them. Implementation sponsored by Turbostream (www.turbostream-cfd.com).

• Calls to Python functions are faster, following the recent "FastCall" optimisations that Victor Stinner implemented for CPython 3.6. See https://bugs.python.org/issue27128 and related issues.

• The new METH_FASTCALL calling convention for PyCFunctions is supported in CPython 3.6. See https://bugs.python.org/issue27810

• Initial support for using Cython modules in Pyston. Patch by Boxiang Sun.

• Dynamic Python attributes are allowed on cdef classes if an attribute cdef dict __dict__ is declared in the class. Patch by empyrical.

• Cython implemented C++ classes can make direct calls to base class methods. Patch by empyrical.

• C++ classes can now have typedef members. STL containers updated with value_type.

• New directive cython.no_gc to fully disable GC for a cdef class. Patch by Claudio Freire.

• Buffer variables are no longer excluded from locals(). Patch by David Woods.

• Building f-strings is faster, especially when formatting C integers.

• for-loop iteration over "std::string".

• libc/math.pxd provides e and pi as alias constants to simplify usage as a drop-in replacement for Python's math module.

• Speed up cython.inline().

• Binary lshift operations with small constant Python integers are faster.

• Some integer operations on Python long objects are faster in Python 2.7.

• Support for the C++ typeid operator.

• Support for bazel using a the pyx_library rule in //Tools:rules.bzl.

Significant Bugs fixed

• Division of complex numbers avoids overflow by using Smith's method.

• Some function signatures in libc.math and numpy.pxd were incorrect. Patch by Michael Seifert.

Other changes

• The "%%cython" IPython/jupyter magic now defaults to the language level of the current jupyter kernel. The language level can be set explicitly with "%%cython -2" or "%%cython -3".

• The distutils extension Cython.Distutils.build_ext has now been updated to use cythonize which properly handles dependencies. The old extension can still be found in Cython.Distutils.old_build_ext and is now deprecated.

• directive_defaults is no longer available in Cython.Compiler.Options, use get_directive_defaults() instead.

Bugs fixed

• IPython cell magic was lacking a good way to enable Python 3 code semantics. It can now be used as "%%cython -3".

• Follow a recent change in PEP 492 and CPython 3.5.2 that now requires the __aiter__() method of asynchronous iterators to be a simple def method instead of an async def method.

• Coroutines and generators were lacking the __module__ special attribute.

• C++ std::complex values failed to auto-convert from and to Python complex objects.

• Namespaced C++ types could not be used as memory view types due to lack of name mangling. Patch by Ivan Smirnov.

• Assignments between identical C++ types that were declared with differently typedefed template types could fail.

• Rebuilds could fail to evaluate dependency timestamps in C++ mode. Patch by Ian Henriksen.

• Macros defined in the distutils compiler option do not require values anymore. Patch by Ian Henriksen.

• Minor fixes for MSVC, Cygwin and PyPy.

Features added

• PEP 498: Literal String Formatting (f-strings). Original patch by Jelle Zijlstra.

• PEP 515: Underscores as visual separators in number literals.

• Parser was adapted to some minor syntax changes in Py3.6, e.g. https://bugs.python.org/issue9232

• The embedded C code comments that show the original source code can be discarded with the new directive emit_code_comments=False.

• Cpdef enums are now first-class iterable, callable types in Python.

• Ctuples can now be declared in pure Python code.

• Posix declarations for DLL loading and stdio extensions were added. Patch by Lars Buitinck.

• The Py2-only builtins unicode(), xrange(), reduce() and long are now also available in compile time DEF expressions when compiling with Py3.

• Exception type tests have slightly lower overhead. This fixes ticket 868.

• @property syntax fully supported in cdef classes, old syntax deprecated.

• C++ classes can now be declared with default template parameters.

Bugs fixed

• C++ exceptions raised by overloaded C++ operators were not always handled. Patch by Ian Henriksen.

• C string literals were previously always stored as non-const global variables in the module. They are now stored as global constants when possible, and otherwise as non-const C string literals in the generated code that uses them. This improves compatibility with strict C compiler options and prevents non-const strings literals with the same content from being incorrectly merged.

• Compile time evaluated str expressions (DEF) now behave in a more useful way by turning into Unicode strings when compiling under Python 3. This allows using them as intermediate values in expressions. Previously, they always evaluated to bytes objects.

• isinf() declarations in libc/math.pxd and numpy/math.pxd now reflect the actual tristate int return value instead of using bint.

• Literal assignments to ctuples avoid Python tuple round-trips in some more corner cases.

• Iteration over dict(...).items() failed to get optimised when dict arguments included keyword arguments.

• cProfile now correctly profiles cpdef functions and methods.

• Compile errors and warnings in integer type conversion code. This fixes ticket 877. Patches by Christian Neukirchen, Nikolaus Rath, Ian Henriksen.

• Reference leak when *args argument was reassigned in closures.

• Truth-testing Unicode strings could waste time and memory in Py3.3+.

• Return values of async functions could be ignored and replaced by None.

• Compiler crash in CPython 3.6.

• Fix prange() to behave identically to range(). The end condition was miscalculated when the range was not exactly divisible by the step.

• Optimised all(genexpr)/any(genexpr) calls could warn about unused code. This fixes ticket 876.

Bugs fixed

• Memory leak when calling Python functions in PyPy.

• Compilation problem with MSVC in C99-ish mode.

• Warning about unused values in a helper macro.

Bugs fixed

• Invalid C code for some builtin methods. This fixes ticket 856 again.

• Incorrect C code in helper functions for PyLong conversion and string decoding. This fixes ticket 863, ticket 864 and ticket 865. Original patch by Nikolaus Rath.

• Large folded or inserted integer constants could use too small C integer types and thus trigger a value wrap-around.

Other changes

• The coroutine and generator types of Cython now also register directly with the Coroutine and Generator ABCs in the backports_abc module if it can be imported. This fixes ticket 870.

Bugs fixed

• Compiler crash when analysing some optimised expressions.

• Coverage plugin was adapted to coverage.py 4.0 beta 2.

• C++ destructor calls could fail when '&' operator is overwritten.

• Incorrect C literal generation for large integers in compile-time evaluated DEF expressions and constant folded expressions.

• Byte string constants could end up as Unicode strings when originating from compile-time evaluated DEF expressions.

• Invalid C code when caching known builtin methods. This fixes ticket 860.

• ino_t in posix.types was not declared as unsigned.

• Declarations in libcpp/memory.pxd were missing operator!(). Patch by Leo Razoumov.

• Static cdef methods can now be declared in .pxd files.

Bugs fixed

• Invalid C code for generators. This fixes ticket 858.

• Invalid C code for some builtin methods. This fixes ticket 856.

• Invalid C code for unused local buffer variables. This fixes ticket 154.

• Test failures on 32bit systems. This fixes ticket 857.

• Code that uses from xyz import * and global C struct/union/array variables could fail to compile due to missing helper functions. This fixes ticket 851.

• Misnamed PEP 492 coroutine property cr_yieldfrom renamed to cr_await to match CPython.

• Missing deallocation code for C++ object attributes in certain extension class hierarchies.

• Crash when async coroutine was not awaited.

• Compiler crash on yield in signature annotations and default argument values. Both are forbidden now.

• Compiler crash on certain constructs in finally clauses.

• Cython failed to build when CPython's pgen is installed.

Features added

• PEP 492 (async/await) was implemented.

• PEP 448 (Additional Unpacking Generalizations) was implemented.

• Support for coverage.py 4.0+ can be enabled by adding the plugin "Cython.Coverage" to the ".coveragerc" config file.

• Annotated HTML source pages can integrate (XML) coverage reports.

• Tracing is supported in nogil functions/sections and module init code.

• When generators are used in a Cython module and the module imports the modules "inspect" and/or "asyncio", Cython enables interoperability by patching these modules during the import to recognise Cython's internal generator and coroutine types. This can be disabled by C compiling the module with "-D CYTHON_PATCH_ASYNCIO=0" or "-D CYTHON_PATCH_INSPECT=0"

• When generators or coroutines are used in a Cython module, their types are registered with the Generator and Coroutine ABCs in the collections or collections.abc stdlib module at import time to enable interoperability with code that needs to detect and process Python generators/coroutines. These ABCs were added in CPython 3.5 and are available for older Python versions through the backports_abc module on PyPI. See https://bugs.python.org/issue24018

• Adding/subtracting/dividing/modulus and equality comparisons with constant Python floats and small integers are faster.

• Binary and/or/xor/rshift operations with small constant Python integers are faster.

• When called on generator expressions, the builtins all(), any(), dict(), list(), set(), sorted() and unicode.join() avoid the generator iteration overhead by inlining a part of their functionality into the for-loop.

• Keyword argument dicts are no longer copied on function entry when they are not being used or only passed through to other function calls (e.g. in wrapper functions).

• The PyTypeObject declaration in cpython.object was extended.

• The builtin type type is now declared as PyTypeObject in source, allowing for extern functions taking type parameters to have the correct C signatures. Note that this might break code that uses type just for passing around Python types in typed variables. Removing the type declaration provides a backwards compatible fix.

• wraparound() and boundscheck() are available as no-ops in pure Python mode.

• Const iterators were added to the provided C++ STL declarations.

• Smart pointers were added to the provided C++ STL declarations. Patch by Daniel Filonik.

• NULL is allowed as default argument when embedding signatures. This fixes ticket 843.

• When compiling with --embed, the internal module name is changed to __main__ to allow arbitrary program names, including those that would be invalid for modules. Note that this prevents reuse of the generated C code as an importable module.

• External C++ classes that overload the assignment operator can be used. Patch by Ian Henriksen.

• Support operator bool() for C++ classes so they can be used in if statements.

Bugs fixed

• Calling "yield from" from Python on a Cython generator that returned a value triggered a crash in CPython. This is now being worked around. See https://bugs.python.org/issue23996

• Language level 3 did not enable true division (a.k.a. float division) for integer operands.

• Functions with fused argument types that included a generic 'object' fallback could end up using that fallback also for other explicitly listed object types.

• Relative cimports could accidentally fall back to trying an absolute cimport on failure.

• The result of calling a C struct constructor no longer requires an intermediate assignment when coercing to a Python dict.

• C++ exception declarations with mapping functions could fail to compile when pre-declared in .pxd files.

• cpdef void methods are now permitted.

• abs(cint) could fail to compile in MSVC and used sub-optimal code in C++. Patch by David Vierra, original patch by Michael Enßlin.

• Buffer index calculations using index variables with small C integer types could overflow for large buffer sizes. Original patch by David Vierra.

• C unions use a saner way to coerce from and to Python dicts.

• When compiling a module foo.pyx, the directories in sys.path are no longer searched when looking for foo.pxd. Patch by Jeroen Demeyer.

• Memory leaks in the embedding main function were fixed. Original patch by Michael Enßlin.

• Some complex Python expressions could fail to compile inside of finally clauses.

• Unprefixed 'str' literals were not supported as C varargs arguments.

• Fixed type errors in conversion enum types to/from Python. Note that this imposes stricter correctness requirements on enum declarations.

Other changes

• Changed mangling scheme in header files generated by cdef api declarations.

• Installation under CPython 3.3+ no longer requires a pass of the 2to3 tool. This also makes it possible to run Cython in Python 3.3+ from a source checkout without installing it first. Patch by Petr Viktorin.

• jedi-typer.py (in Tools/) was extended and renamed to jedityper.py (to make it importable) and now works with and requires Jedi 0.9. Patch by Tzer-jen Wei.

Bugs fixed

• Crash when returning values on generator termination.

• In some cases, exceptions raised during internal isinstance() checks were not propagated.

• Runtime reported file paths of source files (e.g for profiling and tracing) are now relative to the build root directory instead of the main source file.

• Tracing exception handling code could enter the trace function with an active exception set.

• The internal generator function type was not shared across modules.

• Comparisons of (inferred) ctuples failed to compile.

• Closures inside of cdef functions returning void failed to compile.

• Using const C++ references in intermediate parts of longer expressions could fail to compile.

• C++ exception declarations with mapping functions could fail to compile when pre-declared in .pxd files.

• C++ compilation could fail with an ambiguity error in recent MacOS-X Xcode versions.

• C compilation could fail in pypy3.

• Fixed a memory leak in the compiler when compiling multiple modules.

• When compiling multiple modules, external library dependencies could leak into later compiler runs. Fix by Jeroen Demeyer. This fixes ticket 845.

Features added

• C functions can coerce to Python functions, which allows passing them around as callable objects.

• C arrays can be assigned by value and auto-coerce from Python iterables and to Python lists (and tuples).

• Extern C functions can now be declared as cpdef to export them to the module's Python namespace. Extern C functions in pxd files export their values to their own module, iff it exists.

• Anonymous C tuple types can be declared as (ctype1, ctype2, ...).

• PEP 479: turn accidental StopIteration exceptions that exit generators into a RuntimeError, activated with future import "generator_stop".

• Looping over reversed(range()) is optimised in the same way as range(). Patch by Favian Contreras.

Bugs fixed

• Mismatching 'except' declarations on signatures in .pxd and .pyx files failed to produce a compile error.

• Failure to find any files for the path pattern(s) passed into cythonize() is now an error to more easily detect accidental typos.

• The logaddexp family of functions in numpy.math now has correct declarations.

• In Py2.6/7 and Py3.2, simple Cython memory views could accidentally be interpreted as non-contiguous by CPython, which could trigger a CPython bug when copying data from them, thus leading to data corruption. See CPython issues 12834 and 23349.

Other changes

• Preliminary support for defining the Cython language with a formal grammar. To try parsing your files against this grammar, use the --formal_grammar directive. Experimental.

• _ is no longer considered a cacheable builtin as it could interfere with gettext.

• Cythonize-computed metadata now cached in the generated C files.

• Several corrections and extensions in numpy, cpython, and libcpp pxd files.

Bugs fixed

• Crash when assigning a C value to both a Python and C target at the same time.

• Automatic coercion from C++ strings to str generated incomplete code that failed to compile.

• Declaring a constructor in a C++ child class erroneously required a default constructor declaration in the super class.

• resize_smart() in cpython.array was broken.

• Functions in libcpp.cast are now declared as nogil.

• Some missing C-API declarations were added.

• Py3 main code in embedding program code was lacking casts.

• Exception related to distutils "Distribution" class type in pyximport under latest CPython 2.7 and 3.4 releases when setuptools is being imported later.

Features added

• New cythonize option -a to generate the annotated HTML source view.

• Missing C-API declarations in cpython.unicode were added.

• Passing language='c++' into cythonize() globally enables C++ mode for all modules that were not passed as Extension objects (i.e. only source files and file patterns).

• Py_hash_t is a known type (used in CPython for hash values).

• PySlice_*() C-API functions are available from the cpython.slice module.

• Allow arrays of C++ classes.

Bugs fixed

• Reference leak for non-simple Python expressions in boolean and/or expressions.

• To fix a name collision and to reflect availability on host platforms, standard C declarations [ clock(), time(), struct tm and tm* functions ] were moved from posix/time.pxd to a new libc/time.pxd. Patch by Charles Blake.

• Rerunning unmodified modules in IPython's cython support failed. Patch by Matthias Bussonier.

• Casting C++ std::string to Python byte strings failed when auto-decoding was enabled.

• Fatal exceptions in global module init code could lead to crashes if the already created module was used later on (e.g. through a stale reference in sys.modules or elsewhere).

• cythonize.py script was not installed on MS-Windows.

Other changes

• Compilation no longer fails hard when unknown compilation options are passed. Instead, it raises a warning and ignores them (as it did silently before 0.21). This will be changed back to an error in a future release.

Features added

• C (cdef) functions allow inner Python functions.

• Enums can now be declared as cpdef to export their values to the module's Python namespace. Cpdef enums in pxd files export their values to their own module, iff it exists.

• Allow @staticmethod decorator to declare static cdef methods. This is especially useful for declaring "constructors" for cdef classes that can take non-Python arguments.

• Taking a char* from a temporary Python string object is safer in more cases and can be done inside of non-trivial expressions, including arguments of a function call. A compile time error is raised only when such a pointer is assigned to a variable and would thus exceed the lifetime of the string itself.

• Generators have new properties __name__ and __qualname__ that provide the plain/qualified name of the generator function (following CPython 3.5). See https://bugs.python.org/issue21205

• The inline function modifier is available as a decorator @cython.inline in pure mode.

• When cygdb is run in a virtualenv, it enables the same virtualenv inside of the debugger. Patch by Marc Abramowitz.

• PEP 465: dedicated infix operator for matrix multiplication (A @ B).

• HTML output of annotated code uses Pygments for code highlighting and generally received a major overhaul by Matthias Bussonier.

• IPython magic support is now available directly from Cython with the command "%load_ext cython". Cython code can directly be executed in a cell when marked with "%%cython". Code analysis is available with "%%cython -a". Patch by Martín Gaitán.

• Simple support for declaring Python object types in Python signature annotations. Currently requires setting the compiler directive annotation_typing=True.

• New directive use_switch (defaults to True) to optionally disable the optimization of chained if statement to C switch statements.

• Defines dynamic_cast et al. in libcpp.cast and C++ heap data structure operations in libcpp.algorithm.

• Shipped header declarations in posix.* were extended to cover more of the POSIX API. Patches by Lars Buitinck and Mark Peek.

Optimizations

• Simple calls to C implemented Python functions/methods are faster. This also speeds up many operations on builtins that Cython cannot otherwise optimise.

• The "and"/"or" operators try to avoid unnecessary coercions of their arguments. They now evaluate the truth value of each argument independently and only coerce the final result of the whole expression to the target type (e.g. the type on the left side of an assignment). This also avoids reference counting overhead for Python values during evaluation and generally improves the code flow in the generated C code.

• The Python expression "2 ** N" is optimised into bit shifting. See https://bugs.python.org/issue21420

• Cascaded assignments (a = b = ...) try to minimise the number of type coercions.

• Calls to slice() are translated to a straight C-API call.

Bugs fixed

• Crash when assigning memory views from ternary conditional expressions.

• Nested C++ templates could lead to unseparated ">>" characters being generated into the C++ declarations, which older C++ compilers could not parse.

• Sending SIGINT (Ctrl-C) during parallel cythonize() builds could hang the child processes.

• No longer ignore local setup.cfg files for distutils in pyximport. Patch by Martin Teichmann.

• Taking a char* from an indexed Python string generated unsafe reference counting code.

• Set literals now create all of their items before trying to add them to the set, following the behaviour in CPython. This makes a difference in the rare case that the item creation has side effects and some items are not hashable (or if hashing them has side effects, too).

• Cython no longer generates the cross product of C functions for code that uses memory views of fused types in function signatures (e.g. cdef func(floating[:] a, floating[:] b)). This is considered the expected behaviour by most users and was previously inconsistent with other structured types like C arrays. Code that really wants all type combinations can create the same fused memoryview type under different names and use those in the signature to make it clear which types are independent.

• Names that were unknown at compile time were looked up as builtins at runtime but not as global module names. Trying both lookups helps with globals() manipulation.

• Fixed stl container conversion for typedef element types.

• obj.pop(x) truncated large C integer values of x to Py_ssize_t.

• __init__.pyc is recognised as marking a package directory (in addition to .py, .pyx and .pxd).

• Syntax highlighting in cython-mode.el for Emacs no longer incorrectly highlights keywords found as part of longer names.

• Correctly handle from cython.submodule cimport name.

• Fix infinite recursion when using super with cpdef methods.

• No-args dir() was not guaranteed to return a sorted list.

Other changes

• The header line in the generated C files no longer contains the timestamp but only the Cython version that wrote it. This was changed to make builds more reproducible.

• Removed support for CPython 2.4, 2.5 and 3.1.

• The licensing implications on the generated code were clarified to avoid legal constraints for users.

Features added

• Some optimisations for set/frozenset instantiation.

• Support for C++ unordered_set and unordered_map.

Bugs fixed

• Access to attributes of optimised builtin methods (e.g. [].append.__name__) could fail to compile.

• Memory leak when extension subtypes add a memory view as attribute to those of the parent type without having Python object attributes or a user provided dealloc method.

• Compiler crash on readonly properties in "binding" mode.

• Auto-encoding with c_string_encoding=ascii failed in Py3.3.

• Crash when subtyping freelist enabled Cython extension types with Python classes that use __slots__.

• Freelist usage is restricted to CPython to avoid problems with other Python implementations.

• Memory leak in memory views when copying overlapping, contiguous slices.

• Format checking when requesting non-contiguous buffers from cython.array objects was accidentally omitted in Py3.

• C++ destructor calls in extension types could fail to compile in clang.

• Buffer format validation failed for sequences of strings in structs.

• Docstrings on extension type attributes in .pxd files were rejected.

Bugs fixed

• Build error under recent MacOS-X versions where isspace() could not be resolved by clang.

• List/Tuple literals multiplied by more than one factor were only multiplied by the last factor instead of all.

• Lookups of special methods (specifically for context managers) could fail in Python <= 2.6/3.1.

• Local variables were erroneously appended to the signature introspection of Cython implemented functions with keyword-only arguments under Python 3.

• In-place assignments to variables with inferred Python builtin/extension types could fail with type errors if the result value type was incompatible with the type of the previous value.

• The C code generation order of cdef classes, closures, helper code, etc. was not deterministic, thus leading to high code churn.

• Type inference could fail to deduce C enum types.

• Type inference could deduce unsafe or inefficient types from integer assignments within a mix of inferred Python variables and integer variables.

Features added

• Support for CPython 3.4.

• Support for calling C++ template functions.

• yield is supported in finally clauses.

• The C code generated for finally blocks is duplicated for each exit case to allow for better optimisations by the C compiler.

• Cython tries to undo the Python optimisationism of assigning a bound method to a local variable when it can generate better code for the direct call.

• Constant Python float values are cached.

• String equality comparisons can use faster type specific code in more cases than before.

• String/Unicode formatting using the '%' operator uses a faster C-API call.

• bytearray has become a known type and supports coercion from and to C strings. Indexing, slicing and decoding is optimised. Note that this may have an impact on existing code due to type inference.

• Using cdef basestring stringvar and function arguments typed as basestring is now meaningful and allows assigning exactly str and unicode objects, but no subtypes of these types.

• Support for the __debug__ builtin.

• Assertions in Cython compiled modules are disabled if the running Python interpreter was started with the "-O" option.

• Some types that Cython provides internally, such as functions and generators, are now shared across modules if more than one Cython implemented module is imported.

• The type inference algorithm works more fine granular by taking the results of the control flow analysis into account.

• A new script in bin/cythonize provides a command line frontend to the cythonize() compilation function (including distutils build).

• The new extension type decorator @cython.no_gc_clear prevents objects from being cleared during cyclic garbage collection, thus making sure that object attributes are kept alive until deallocation.

• During cyclic garbage collection, attributes of extension types that cannot create reference cycles due to their type (e.g. strings) are no longer considered for traversal or clearing. This can reduce the processing overhead when searching for or cleaning up reference cycles.

• Package compilation (i.e. __init__.py files) now works, starting with Python 3.3.

• The cython-mode.el script for Emacs was updated. Patch by Ivan Andrus.

• An option common_utility_include_dir was added to cythonize() to save oft-used utility code once in a separate directory rather than as part of each generated file.

• unraisable_tracebacks directive added to control printing of tracebacks of unraisable exceptions.

Bugs fixed

• Abstract Python classes that subtyped a Cython extension type failed to raise an exception on instantiation, and thus ended up being instantiated.

• set.add(a_tuple) and set.discard(a_tuple) failed with a TypeError in Py2.4.

• The PEP 3155 __qualname__ was incorrect for nested classes and inner classes/functions declared as global.

• Several corner cases in the try-finally statement were fixed.

• The metaclass of a Python class was not inherited from its parent class(es). It is now extracted from the list of base classes if not provided explicitly using the Py3 metaclass keyword argument. In Py2 compilation mode, a __metaclass__ entry in the class dict will still take precedence if not using Py3 metaclass syntax, but only after creating the class dict (which may have been done by a metaclass of a base class, see PEP 3115). It is generally recommended to use the explicit Py3 syntax to define metaclasses for Python types at compile time.

• The automatic C switch statement generation behaves more safely for heterogeneous value types (e.g. mixing enum and char), allowing for a slightly wider application and reducing corner cases. It now always generates a 'default' clause to avoid C compiler warnings about unmatched enum values.

• Fixed a bug where class hierarchies declared out-of-order could result in broken generated code.

• Fixed a bug which prevented overriding const methods of C++ classes.

• Fixed a crash when converting Python objects to C++ strings fails.

Other changes

• In Py3 compilation mode, Python2-style metaclasses declared by a __metaclass__ class dict entry are ignored.

• In Py3.4+, the Cython generator type uses tp_finalize() for safer cleanup instead of tp_del().

Features added

Bugs fixed

• Some standard declarations were fixed or updated, including the previously incorrect declaration of PyBuffer_FillInfo() and some missing bits in libc.math.

• Heap allocated subtypes of type used the wrong base type struct at the C level.

• Calling the unbound method dict.keys/value/items() in dict subtypes could call the bound object method instead of the unbound supertype method.

• "yield" wasn't supported in "return" value expressions.

• Using the "bint" type in memory views lead to unexpected results. It is now an error.

• Assignments to global/closure variables could catch them in an illegal state while deallocating the old value.

Other changes

Features added

• Completely empty C-API structs for extension type slots (protocols like number/mapping/sequence) are no longer generated into the C code.

• Docstrings that directly follow a public/readonly attribute declaration in a cdef class will be used as docstring of the auto-generated property. This fixes ticket 206.

• The automatic signature documentation tries to preserve more semantics of default arguments and argument types. Specifically, bint arguments now appear as type bool.

• A warning is emitted when negative literal indices are found inside of a code section that disables wraparound handling. This helps with fixing invalid code that might fail in the face of future compiler optimisations.

• Constant folding for boolean expressions (and/or) was improved.

• Added a build_dir option to cythonize() which allows one to place the generated .c files outside the source tree.

Bugs fixed

• isinstance(X, type) failed to get optimised into a call to PyType_Check(), as done for other builtin types.

• A spurious from datetime cimport * was removed from the "cpython" declaration package. This means that the "datetime" declarations (added in 0.19) are no longer available directly from the "cpython" namespace, but only from "cpython.datetime". This is the correct way of doing it because the declarations refer to a standard library module, not the core CPython C-API itself.

• The C code for extension types is now generated in topological order instead of source code order to avoid C compiler errors about missing declarations for subtypes that are defined before their parent.

• The memoryview type name no longer shows up in the module dict of modules that use memory views. This fixes trac ticket 775.

• Regression in 0.19 that rejected valid C expressions from being used in C array size declarations.

• In C++ mode, the C99-only keyword restrict could accidentally be seen by the GNU C++ compiler. It is now specially handled for both GCC and MSVC.

• Testing large (> int) C integer values for their truth value could fail due to integer wrap-around.

Other changes

Features added

• New directives c_string_type and c_string_encoding to more easily and automatically convert between C strings and the different Python string types.

• The extension type flag Py_TPFLAGS_HAVE_VERSION_TAG is enabled by default on extension types and can be disabled using the type_version_tag compiler directive.

• EXPERIMENTAL support for simple Cython code level line tracing. Enabled by the "linetrace" compiler directive.

• Cython implemented functions make their argument and return type annotations available through the __annotations__ attribute (PEP 3107).

• Access to non-cdef module globals and Python object attributes is faster.

• Py_UNICODE* coerces from and to Python unicode strings. This is helpful when talking to Windows APIs, which use compatible wchar_t arrays for strings. Note that the Py_UNICODE type is otherwise deprecated as of CPython 3.3.

• isinstance(obj, basestring) is optimised. In Python 3 it only tests for instances of str (i.e. Py2 unicode).

• The basestring builtin is mapped to str (i.e. Py2 unicode) when compiling the generated C code under Python 3.

• Closures use freelists, which can speed up their creation quite substantially. This is also visible for short running generator expressions, for example.

• A new class decorator @cython.freelist(N) creates a static freelist of N instances for an extension type, thus avoiding the costly allocation step if possible. This can speed up object instantiation by 20-30% in suitable scenarios. Note that freelists are currently only supported for base types, not for types that inherit from others.

• Fast extension type instantiation using the Type.__new__(Type) idiom has gained support for passing arguments. It is also a bit faster for types defined inside of the module.

• The Python2-only dict methods .iter*() and .view*() (requires Python 2.7) are automatically mapped to the equivalent keys/values/items methods in Python 3 for typed dictionaries.

• Slicing unicode strings, lists and tuples is faster.

• list.append() is faster on average.

• raise Exception() from None suppresses the exception context in Py3.3.

• Py3 compatible exec(tuple) syntax is supported in Py2 code.

• Keyword arguments are supported for cdef functions.

• External C++ classes can be declared nogil. Patch by John Stumpo. This fixes trac ticket 805.

Bugs fixed

• 2-value slicing of unknown objects passes the correct slice when the getitem protocol is used instead of the getslice protocol (especially in Python 3), i.e. None values for missing bounds instead of [0,maxsize]. It is also a bit faster in some cases, e.g. for constant bounds. This fixes trac ticket 636.

• Cascaded assignments of None values to extension type variables failed with a TypeError at runtime.

• The __defaults__ attribute was not writable for Cython implemented functions.

• Default values of keyword-only arguments showed up in __defaults__ instead of __kwdefaults__ (which was not implemented). Both are available for Cython implemented functions now, as specified in Python 3.x.

• yield works inside of with gil sections. It previously lead to a crash. This fixes trac ticket 803.

• Static methods without explicitly named positional arguments (e.g. having only *args) crashed when being called. This fixes trac ticket 804.

• dir() without arguments previously returned an unsorted list, which now gets sorted as expected.

• dict.items(), dict.keys() and dict.values() no longer return lists in Python 3.

• Exiting from an except-as clause now deletes the exception in Python 3 mode.

• The declarations of frexp() and ldexp() in math.pxd were incorrect.

Other changes

Features added

• Named Unicode escapes ("N{...}") are supported.

• Python functions/classes provide the special attribute "__qualname__" as defined by PEP 3155.

• Added a directive overflowcheck which raises an OverflowException when arithmetic with C ints overflow. This has a modest performance penalty, but is much faster than using Python ints.

• Calls to nested Python functions are resolved at compile time.

• Type inference works across nested functions.

• py_bytes_string.decode(...) is optimised.

• C const declarations are supported in the language.

Bugs fixed

• Automatic C++ exception mapping didn't work in nogil functions (only in "with nogil" blocks).

Other changes

Bugs fixed

• Garbage collection triggered during deallocation of container classes could lead to a double-deallocation.