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Allocating extra data after an object instance #103743
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Co-authored-by: Petr Viktorin <[email protected]> Co-authored-by: Erlend E. Aasland <[email protected]>
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* main: pythongh-103822: [Calendar] change return value to enum for day and month APIs (pythonGH-103827) pythongh-65022: Fix description of tuple return value in copyreg (python#103892) pythonGH-103525: Improve exception message from `pathlib.PurePath()` (pythonGH-103526) pythongh-84436: Add integration C API tests for immortal objects (pythongh-103962) pythongh-103743: Add PyUnstable_Object_GC_NewWithExtraData (pythonGH-103744) pythongh-102997: Update Windows installer to SQLite 3.41.2. (python#102999) pythonGH-103484: Fix redirected permanently URLs (python#104001) Improve assert_type phrasing (python#104081) pythongh-102997: Update macOS installer to SQLite 3.41.2. (pythonGH-102998) pythonGH-103472: close response in HTTPConnection._tunnel (python#103473) pythongh-88496: IDLE - fix another test on macOS (python#104075) pythongh-94673: Hide Objects in PyTypeObject Behind Accessors (pythongh-104074) pythongh-94673: Properly Initialize and Finalize Static Builtin Types for Each Interpreter (pythongh-104072) pythongh-104016: Skip test for deeply neste f-strings on wasi (python#104071)
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* main: (760 commits) pythonGH-104102: Optimize `pathlib.Path.glob()` handling of `../` pattern segments (pythonGH-104103) pythonGH-104104: Optimize `pathlib.Path.glob()` by avoiding repeated calls to `os.path.normcase()` (pythonGH-104105) pythongh-103822: [Calendar] change return value to enum for day and month APIs (pythonGH-103827) pythongh-65022: Fix description of tuple return value in copyreg (python#103892) pythonGH-103525: Improve exception message from `pathlib.PurePath()` (pythonGH-103526) pythongh-84436: Add integration C API tests for immortal objects (pythongh-103962) pythongh-103743: Add PyUnstable_Object_GC_NewWithExtraData (pythonGH-103744) pythongh-102997: Update Windows installer to SQLite 3.41.2. (python#102999) pythonGH-103484: Fix redirected permanently URLs (python#104001) Improve assert_type phrasing (python#104081) pythongh-102997: Update macOS installer to SQLite 3.41.2. (pythonGH-102998) pythonGH-103472: close response in HTTPConnection._tunnel (python#103473) pythongh-88496: IDLE - fix another test on macOS (python#104075) pythongh-94673: Hide Objects in PyTypeObject Behind Accessors (pythongh-104074) pythongh-94673: Properly Initialize and Finalize Static Builtin Types for Each Interpreter (pythongh-104072) pythongh-104016: Skip test for deeply neste f-strings on wasi (python#104071) pythongh-104057: Fix direct invocation of test_super (python#104064) pythongh-87092: Expose assembler to unit tests (python#103988) pythongh-97696: asyncio eager tasks factory (python#102853) pythongh-84436: Immortalize in _PyStructSequence_InitBuiltinWithFlags() (pythongh-104054) ...
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…ExtraData Summary: `_PyObject_GC_Malloc` has gone away in 3.12, but I think the reason we're using it - adding extra data to a GC-managed `PyObject*` - is covered by the recently added `PyUnstable_Object_GC_NewWithExtraData`. The future of this [is a little uncertain](python/cpython#103743) but for now it seems to do what we want. Reviewed By: alexmalyshev Differential Revision: D60684943 fbshipit-source-id: d6b8fb001502c68805bd7edd31fdec61eb9389bb
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Feature or enhancement
Add an unstable (in PEP 689 sense) function that allocates memory for a GC object and allows the caller to specify the size of additional memory that should be allocated after the object. Similar to what could be done using
_PyObject_GC_Malloc
function in Python <= 3.10.Pitch
Currently there is no way of allocating extra data after an object and still being able to have a standard Python class that supports GC, allows inheriting and doesn't come with limitations of
PyVarObject
(see #103740).See the linked discussion for more details, but in essence the use case is the following. We have a base class and metaclass that support defining "slots" on classes (similar to Python
__slots__
, but with a different behavior, more on that later). The data for the slots is stored after the object, in the same block of memory. When inheriting from a class that defines such "slots", the subclass gets all the slots from its base classes + slots defined on it. The data for all those slots is always stored after the object, so the slot storage size doesn't really come into calculation fortp_basicsize
.A nice effect of this behavior is that a subclass can inherit from multiple classes with each of the bases defining its own slots. The subclass then gets all those slots, as if they were directly defined on it (in contrast with Python
__slots__
, which prevents such inheritance).CC: @encukou
Previous discussion
See this discussion for more details.
Linked PRs
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