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CHANGES.rst

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    Cython Changelog

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

    Features added

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

    Bugs fixed

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

    Other changes

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

    3.0.0 alpha 5 (2020-05-19)

    Features added

    • .pxd files can now be versioned by adding an extension like ".cython-30.pxd" to prevent older Cython versions (than 3.0 in this case) from picking them up. (Github issue #3577)
    • Several macros/functions declared in the NumPy API are now usable without holding the GIL.
    • libc.math was extended to include all C99 function declarations. Patch by Dean Scarff. (Github issue #3570)

    Bugs fixed

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

    3.0.0 alpha 4 (2020-05-05)

    Features added

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

    Bugs fixed

    • Exception position reporting could run into race conditions on threaded code. It now uses function-local variables again.
    • Error handling early in the module init code could lead to a crash.
    • Error handling in cython.array creation was improved to avoid calling C-API functions with an error held.
    • Complex buffer item types of structs of arrays could fail to validate. Patch by Leo and smutch. (Github issue #1407)
    • When importing the old Cython build_ext integration with distutils, the additional command line arguments leaked into the regular command. Patch by Kamekameha. (Github issue #2209)
    • The improved GIL handling in nogil functions introduced in 3.0a3 could generate invalid C code. (Github issue #3558)
    • PyEval_InitThreads() is no longer used in Py3.7+ where it is a no-op.
    • Parallel builds of Cython itself (setup.py build_ext -j N) failed on Windows.

    Other changes

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

    3.0.0 alpha 3 (2020-04-27)

    Features added

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

    Bugs fixed

    • Includes all bug-fixes from the 0.29.17 release.

    3.0.0 alpha 2 (2020-04-23)

    Features added

    • std::move() is now used in C++ mode for internal temp variables to make them work without copying values. Patch by David Woods. (Github issues #3253, 1612)
    • __class_getitem__ is supported for types on item access (PEP-560). Patch by msg555. (Github issue #2753)
    • The simplified Py3.6 customisation of class creation is implemented (PEP-487). (Github issue #2781)
    • Conditional blocks in Python code that depend on cython.compiled are eliminated at an earlier stage, which gives more freedom in writing replacement Python code. Patch by David Woods. (Github issue #3507)
    • numpy.import_array() is automatically called if numpy has been cimported and it has not been called in the module code. This is intended as a hidden fail-safe so user code should continue to call numpy.import_array. Patch by David Woods. (Github issue #3524)
    • The Cython AST code serialiser class CodeWriter in Cython.CodeWriter supports more syntax nodes.
    • The fastcall/vectorcall protocols are used for several internal Python calls. (Github issue #3540)

    Bugs fixed

    • With language_level=3/3str, Python classes without explicit base class are now new-style (type) classes also in Py2. Previously, they were created as old-style (non-type) classes. (Github issue #3530)
    • C++ typeid() failed for fused types. Patch by David Woods. (Github issue #3203)
    • __arg argument names in methods were not mangled with the class name. Patch by David Woods. (Github issue #1382)
    • Creating an empty unicode slice with large bounds could crash. Patch by Sam Sneddon. (Github issue #3531)
    • Decoding an empty bytes/char* slice with large bounds could crash. Patch by Sam Sneddon. (Github issue #3534)
    • Temporary buffer indexing variables were not released and could show up in C compiler warnings, e.g. in generators. Patch by David Woods. (Github issues #3430, #3522)
    • Several C compiler warnings were fixed.

    3.0.0 alpha 1 (2020-04-12)

    Features added

    • Cython functions now use the PEP-590 vectorcall protocol in Py3.7+. Patch by Jeroen Demeyer. (Github issue #2263)
    • Unicode identifiers are supported in Cython code (PEP 3131). Patch by David Woods. (Github issue #2601)
    • Unicode module names and imports are supported. Patch by David Woods. (Github issue #3119)
    • Annotations are no longer parsed, keeping them as strings following PEP-563. Patch by David Woods. (Github issue #3285)
    • Preliminary support for the CPython's Py_LIMITED_API (stable ABI) is available by setting the CYTHON_LIMITED_API C macro. Note that the support is currently in an early stage and many features do not yet work. Patches by Eddie Elizondo and David Woods. (Github issues #3223, #3311, #3501)
    • The dispatch to fused functions is now linear in the number of arguments, which makes it much faster, often 2x or more, and several times faster for larger fused types with many specialisations. Patch by will-ca. (Github issue #1385)
    • with gil/nogil statements can be conditional based on compile-time constants, e.g. fused type checks. Patch by Noam Hershtig. (Github issue #2579)
    • const can be used together with fused types. Patch by Thomas Vincent. (Github issue #1772)
    • Reimports of already imported modules are substantially faster. (Github issue #2854)
    • Positional-only arguments are supported in Python functions. Patch by Josh Tobin. (Github issue #2915)
    • The volatile C modifier is supported in Cython code. Patch by Jeroen Demeyer. (Github issue #1667)
    • @cython.trashcan(True) can be used on an extension type to enable the CPython trashcan. This allows deallocating deeply recursive objects without overflowing the stack. Patch by Jeroen Demeyer. (Github issue #2842)
    • Inlined properties can be defined for external extension types. Patch by Matti Picus. (Github issue #2640)
    • The str() builtin now calls PyObject_Str() instead of going through a Python call. Patch by William Ayd. (Github issue #3279)
    • String concatenation can now happen in place if possible, by extending the existing string rather than always creating a new one. Patch by David Woods. (Github issue #3453)
    • Multiplication of Python numbers with small constant integers is faster. (Github issue #2808)
    • Some list copying is avoided internally when a new list needs to be created but we already have a fresh one. (Github issue #3494)
    • Extension types that do not need their own tp_new implementation (because they have no object attributes etc.) directly inherit the implementation of their parent type if possible. (Github issue #1555)
    • The attributes gen.gi_frame and coro.cr_frame of Cython compiled generators and coroutines now return an actual frame object for introspection. (Github issue #2306)
    • Several declarations in cpython.*, libc.* and libcpp.* were added. Patches by Jeroen Demeyer, Matthew Edwards, Chris Gyurgyik, Jerome Kieffer and Zackery Spytz. (Github issues #3468, #3332, #3202, #3188, #3179, #2891, #2826, #2713)
    • Deprecated NumPy API usages were removed from numpy.pxd. Patch by Matti Picus. (Github issue #3365)
    • cython.inline() now sets the NPY_NO_DEPRECATED_API=NPY_1_7_API_VERSION C macro automatically when numpy is imported in the code, to avoid C compiler warnings about deprecated NumPy C-API usage.
    • The builtin abs() function can now be used on C numbers in nogil code. Patch by Elliott Sales de Andrade. (Github issue #2748)
    • PEP-479 (generator_stop) is now enabled by default with language level 3. (Github issue #2580)
    • The cython.view.array type supports inheritance. Patch by David Woods. (Github issue #3413)
    • Code annotation accepts a new debugging argument --annotate-fullc that will include the complete syntax highlighted C file in the HTML output. (Github issue #2855)
    • --no-capture added to runtests.py to prevent stdout/stderr capturing during srctree tests. Patch by Matti Picus. (Github issue #2701)
    • --no-docstrings option added to cythonize script. Original patch by mo-han. (Github issue #2889)
    • cygdb gives better error messages when it fails to initialise the Python runtime support in gdb. Patch by Volker Weissmann. (Github issue #3489)
    • The Pythran shape attribute is supported. Patch by Serge Guelton. (Github issue #3307)

    Bugs fixed

    • The unicode methods .upper(), .lower() and .title() were incorrectly optimised for single character input values and only returned the first character if multiple characters should have been returned. They now use the original Python methods again.
    • Fused argument types were not correctly handled in type annotations and cython.locals(). Patch by David Woods. (Github issues #3391, #3142)
    • Diverging from the usual behaviour, len(memoryview), len(char*) and len(Py_UNICODE*) returned an unsigned size_t value. They now return a signed Py_ssize_t, like other usages of len().
    • Nested dict literals in function call kwargs could incorrectly raise an error about duplicate keyword arguments, which are allowed when passing them from dict literals. (Github issue #2963)
    • Item access (subscripting) with integer indices/keys always tried the Sequence protocol before the Mapping protocol, which diverged from Python semantics. It now passes through the Mapping protocol first when supported. (Github issue #1807)
    • Name lookups in class bodies no longer go through an attribute lookup. Patch by Jeroen Demeyer. (Github issue #3100)
    • Broadcast assignments to a multi-dimensional memory view slice could end up in the wrong places when the underlying memory view is known to be contiguous but the slice is not. (Github issue #2941)
    • Pickling unbound methods of Python classes failed. Patch by Pierre Glaser. (Github issue #2972)
    • The Py_hash_t type failed to accept arbitrary "index" values. (Github issue #2752)
    • The first function line number of functions with decorators pointed to the signature line and not the first decorator line, as in Python. Patch by Felix Kohlgrüber. (Github issue #2536)
    • Constant integer expressions that used a negative exponent were evaluated as integer 0 instead of the expected float value. Patch by Kryštof Pilnáček. (Github issue #2133)
    • The cython.declare() and cython.cast() functions could fail in pure mode. Patch by Dmitry Shesterkin. (Github issue #3244)
    • __doc__ was not available inside of the class body during class creation. (Github issue #1635)
    • Setting language_level=2 in a file did not work if language_level=3 was enabled globally before. Patch by Jeroen Demeyer. (Github issue #2791)
    • __init__.pyx files were not always considered as package indicators. (Github issue #2665)
    • Compiling package __init__ files could fail under Windows due to an undefined export symbol. (Github issue #2968)
    • A C compiler cast warning was resolved. Patch by Michael Buesch. (Github issue #2775)
    • Binding staticmethods of Cython functions were not behaving like Python methods. Patch by Jeroen Demeyer. (Github issue #3106, #3102)
    • Memoryviews failed to compile when the cache_builtins feature was disabled. Patch by David Woods. (Github issue #3406)

    Other changes

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

    0.29.21 (2020-0?-??)

    Bugs fixed

    • Fix a regression in 0.29.20 where __div__ failed to be found in extension types. (Github issue #3688)
    • The deprecated C-API function PyUnicode_FromUnicode() is no longer used. Original patch by Inada Naoki. (Github issue #3677)

    0.29.20 (2020-06-10)

    Bugs fixed

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

    0.29.19 (2020-05-20)

    Bugs fixed

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