[Yuvansh-thx]

Fixes gh-160749

Summary of Changes

Clarify the inheritance and default documentation for the tp_alloc and tp_free slots in Doc/c-api/typeobj.rst.

The documentation previously stated that heap subtypes do not inherit tp_alloc or tp_free, and that for heap subtypes, tp_alloc is always set to PyType_GenericAlloc() and tp_free defaults to a generic deallocator.

However, heap types also include types created through C API functions such as PyType_FromSpec and PyType_FromMetaclass. For these types, if Py_tp_alloc or Py_tp_free is omitted from the specification slots, the corresponding slot is inherited from the base type through inherit_slots in Objects/typeobject.c. If the base type defines a custom allocator or deallocator, the C API heap subtype can inherit that custom implementation.

The exception applies to subtypes created using Python’s class statement or the type() constructor, which are handled by type_new_alloc. In these cases, tp_alloc and tp_free are explicitly initialized to PyType_GenericAlloc and PyObject_GC_Del, respectively.

Changes Made

• PyTypeObject.tp_alloc: Clarified that subtypes inherit this slot from the base type, defaulting to PyType_GenericAlloc when inherited from object. Documented the exception for subtypes created using the class statement or type().
• PyTypeObject.tp_free: Clarified that subtypes inherit this slot from the base type, subject to garbage collection compatibility rules. Documented the exception for subtypes created using the class statement or type().
• Default sections: Updated the documentation for both slots to distinguish between types created through Python’s class statement or type() constructor and other subtypes, including static types and C API heap types created through PyType_FromSpec.

Testing

Documentation-only change. No code changes or additional tests are included.

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± c-api/typeobj.html