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gh-95245: Document Py_TPFLAGS_PREHEADER #135861

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Add comemnt for Py_TPFLAGS_PREHEADER
sergey-miryanov Jun 23, 2025
3195c33
Add Py_TPFLAGS_PREHEADER to typeobj.rst
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Update Doc/c-api/typeobj.rst
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12 changes: 12 additions & 0 deletions Doc/c-api/typeobj.rst
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Expand Up @@ -1287,6 +1287,18 @@ and :c:data:`PyType_Type` effectively act as defaults.)
:c:member:`~PyTypeObject.tp_weaklistoffset` field is set in a superclass.


.. c:macro:: Py_TPFLAGS_PREHEADER

A shorthand for checking if VM-managed fields are present.
Currently, this macro is equivalent to
:c:expr:`Py_TPFLAGS_MANAGED_DICT | Py_TPFLAGS_MANAGED_WEAKREF`.

This macro is intended for internal usage only; prefer using individual
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I'm still not a big fan of documenting this as internal-only. If it's in the public headers and documentation, it should be at least usable. How about we say that its value is unstable, so we can change it later?

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What about this?
This macro is intended for internal usage only and may be changed without any notes

Is it OK or you prefer to completely remove the internal usage part?

flags instead.

.. versionadded:: 3.12


.. c:macro:: Py_TPFLAGS_ITEMS_AT_END

Only usable with variable-size types, i.e. ones with non-zero
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3 changes: 3 additions & 0 deletions Include/object.h
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Expand Up @@ -534,6 +534,9 @@ given type object has a specified feature.
*/
#define Py_TPFLAGS_MANAGED_DICT (1 << 4)

/* Type has dictionary or weakref pointers that are managed by VM and has
* to allocate space to store these.
*/
#define Py_TPFLAGS_PREHEADER (Py_TPFLAGS_MANAGED_WEAKREF | Py_TPFLAGS_MANAGED_DICT)

/* Set if instances of the type object are treated as sequences for pattern matching */
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