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gh-139165: Make Py_SIZE, Py_IS_TYPE,Py_ SET_SIZE regular functions in stable ABI #139166

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Merged
encukou merged 9 commits into from
Nov 25, 2025
Merged

gh-139165: Make Py_SIZE, Py_IS_TYPE,Py_ SET_SIZE regular functions in stable ABI #139166

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1bb08c2
Make Py_{SIZE,IS_TYPE,SET_SIZE} regular functions in stable ABI
encukou Sep 10, 2025
9270e96
Merge in the main branch
encukou Sep 22, 2025
0ee604a
Adjust comments
encukou Sep 22, 2025
b5b8c1e
Add blurb
encukou Sep 22, 2025
b522757
Fix reference
encukou Sep 22, 2025
eebcc12
Merge in the main branch
encukou Oct 21, 2025
aee27c9
Update for _Py_OPAQUE_PYOBJECT
encukou Oct 21, 2025
0306b57
Merge in the main branch
encukou Nov 20, 2025
7028056
Note that PyObject fields are part of stable ABI
encukou Nov 20, 2025
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3 changes: 3 additions & 0 deletions Doc/data/stable_abi.dat
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96 changes: 55 additions & 41 deletions Include/object.h
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Original file line number Diff line number Diff line change
Expand Up @@ -140,12 +140,12 @@ struct _object {
# endif
};
#else
Py_ssize_t ob_refcnt;
Py_ssize_t ob_refcnt; // part of stable ABI; do not change
#endif
_Py_ALIGNED_DEF(_PyObject_MIN_ALIGNMENT, char) _aligner;
};

PyTypeObject *ob_type;
PyTypeObject *ob_type; // part of stable ABI; do not change
};
#else
// Objects that are not owned by any thread use a thread id (tid) of zero.
Expand Down Expand Up @@ -173,7 +173,7 @@ struct _object {
#ifndef _Py_OPAQUE_PYOBJECT
struct PyVarObject {
PyObject ob_base;
Py_ssize_t ob_size; /* Number of items in variable part */
Py_ssize_t ob_size; // Number of items in variable part. Part of stable ABI
};
#endif
typedef struct PyVarObject PyVarObject;
Expand Down Expand Up @@ -265,56 +265,72 @@ _Py_IsOwnedByCurrentThread(PyObject *ob)
}
#endif

// Py_TYPE() implementation for the stable ABI
PyAPI_DATA(PyTypeObject) PyLong_Type;
PyAPI_DATA(PyTypeObject) PyBool_Type;

/* Definitions for the stable ABI */
#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= _Py_PACK_VERSION(3, 14)
PyAPI_FUNC(PyTypeObject*) Py_TYPE(PyObject *ob);
#endif
#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= _Py_PACK_VERSION(3, 15)
PyAPI_FUNC(Py_ssize_t) Py_SIZE(PyObject *ob);
PyAPI_FUNC(int) Py_IS_TYPE(PyObject *ob, PyTypeObject *type);
PyAPI_FUNC(void) Py_SET_SIZE(PyVarObject *ob, Py_ssize_t size);
#endif
Comment on lines +275 to +279
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@davidhewitt davidhewitt May 10, 2026

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I'm just checking PyO3's FFI definitions against 3.15b1 and it seems to me that this PR has changed these symbols to always be exported functions on 3.15.

That seems to differ with the issue description, which apparently intended to keep the static inline functions for the non-limited API?

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@vstinner vstinner May 11, 2026

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Extract of object.c in the 3.15 branch:

static inline int
_Py_IS_TYPE_impl(PyObject *ob, PyTypeObject *type)
{
    return Py_TYPE(ob) == type;
}

#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 < _Py_PACK_VERSION(3, 11)
#  define Py_IS_TYPE(ob, type) _Py_IS_TYPE_impl(_PyObject_CAST(ob), (type))
#elif Py_LIMITED_API+0 < _Py_PACK_VERSION(3, 15)
#  define Py_IS_TYPE(ob, type) _Py_IS_TYPE_impl((ob), (type))
#else
// Limited API 3.15+: use function calls
#endif

If Py_LIMITED_API is not defined or if it's defined to Python 3.14 or older, Py_IS_TYPE() is implemented as a static inline function. The code has been modified since this PR.

Would you mind to elaborate which API is implemented as a function call? Using the limited C API or not? Which limited C API version?

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@davidhewitt davidhewitt May 13, 2026

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You're right, sorry for the confusion. I think the tooling I was using to check had a bug, and then I saw this diff and got myself confused. 🤦

Even looking at this diff again, the #define macros just below starting on 292 will implement as a static inline function.

Sorry for the noise!

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@vstinner vstinner May 13, 2026

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No problem. Thanks for double checking.


#ifndef _Py_OPAQUE_PYOBJECT

#if defined(Py_LIMITED_API) && Py_LIMITED_API+0 >= 0x030e0000
// Stable ABI implements Py_TYPE() as a function call
// on limited C API version 3.14 and newer.
static inline void
Py_SET_TYPE(PyObject *ob, PyTypeObject *type)
{
ob->ob_type = type;
}

#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 < _Py_PACK_VERSION(3, 11)
// Non-limited API & limited API 3.11 & below: use static inline functions and
// use _PyObject_CAST so that users don't need their own casts
# define Py_TYPE(ob) _Py_TYPE_impl(_PyObject_CAST(ob))
# define Py_SIZE(ob) _Py_SIZE_impl(_PyObject_CAST(ob))
# define Py_IS_TYPE(ob, type) _Py_IS_TYPE_impl(_PyObject_CAST(ob), (type))
# define Py_SET_SIZE(ob, size) _Py_SET_SIZE_impl(_PyVarObject_CAST(ob), (size))
# define Py_SET_TYPE(ob, type) Py_SET_TYPE(_PyObject_CAST(ob), type)
#elif Py_LIMITED_API+0 < _Py_PACK_VERSION(3, 15)
// Limited API 3.11-3.14: use static inline functions, without casts
# define Py_SIZE(ob) _Py_SIZE_impl(ob)
# define Py_IS_TYPE(ob, type) _Py_IS_TYPE_impl((ob), (type))
# define Py_SET_SIZE(ob, size) _Py_SET_SIZE_impl((ob), (size))
# if Py_LIMITED_API+0 < _Py_PACK_VERSION(3, 14)
// Py_TYPE() is static inline only on Limited API 3.13 and below
# define Py_TYPE(ob) _Py_TYPE_impl(ob)
# endif
#else
static inline PyTypeObject* _Py_TYPE(PyObject *ob)
{
return ob->ob_type;
}
#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 < 0x030b0000
# define Py_TYPE(ob) _Py_TYPE(_PyObject_CAST(ob))
#else
# define Py_TYPE(ob) _Py_TYPE(ob)
#endif
// Limited API 3.15+: use function calls
#endif

PyAPI_DATA(PyTypeObject) PyLong_Type;
PyAPI_DATA(PyTypeObject) PyBool_Type;
static inline
PyTypeObject* _Py_TYPE_impl(PyObject *ob)
{
return ob->ob_type;
}

#ifndef _Py_OPAQUE_PYOBJECT
// bpo-39573: The Py_SET_SIZE() function must be used to set an object size.
static inline Py_ssize_t Py_SIZE(PyObject *ob) {
static inline Py_ssize_t
_Py_SIZE_impl(PyObject *ob)
{
assert(Py_TYPE(ob) != &PyLong_Type);
assert(Py_TYPE(ob) != &PyBool_Type);
return _PyVarObject_CAST(ob)->ob_size;
}
#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 < 0x030b0000
# define Py_SIZE(ob) Py_SIZE(_PyObject_CAST(ob))
#endif
#endif // !defined(_Py_OPAQUE_PYOBJECT)

static inline int Py_IS_TYPE(PyObject *ob, PyTypeObject *type) {
static inline int
_Py_IS_TYPE_impl(PyObject *ob, PyTypeObject *type)
{
return Py_TYPE(ob) == type;
}
#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 < 0x030b0000
# define Py_IS_TYPE(ob, type) Py_IS_TYPE(_PyObject_CAST(ob), (type))
#endif


#ifndef _Py_OPAQUE_PYOBJECT
static inline void Py_SET_TYPE(PyObject *ob, PyTypeObject *type) {
ob->ob_type = type;
}
#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 < 0x030b0000
# define Py_SET_TYPE(ob, type) Py_SET_TYPE(_PyObject_CAST(ob), type)
#endif

static inline void Py_SET_SIZE(PyVarObject *ob, Py_ssize_t size) {
static inline void
_Py_SET_SIZE_impl(PyVarObject *ob, Py_ssize_t size)
{
assert(Py_TYPE(_PyObject_CAST(ob)) != &PyLong_Type);
assert(Py_TYPE(_PyObject_CAST(ob)) != &PyBool_Type);
#ifdef Py_GIL_DISABLED
Expand All @@ -323,9 +339,7 @@ static inline void Py_SET_SIZE(PyVarObject *ob, Py_ssize_t size) {
ob->ob_size = size;
#endif
}
#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 < 0x030b0000
# define Py_SET_SIZE(ob, size) Py_SET_SIZE(_PyVarObject_CAST(ob), (size))
#endif

#endif // !defined(_Py_OPAQUE_PYOBJECT)


Expand Down
3 changes: 3 additions & 0 deletions Lib/test/test_stable_abi_ctypes.py
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/C_API/2025-09-22-16-32-00.gh-issue-139165.6Czn7S.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Expose the functions :c:func:`Py_SIZE`, :c:func:`Py_IS_TYPE` and
:c:func:`Py_SET_SIZE` in the Stable ABI.
11 changes: 11 additions & 0 deletions Misc/stable_abi.toml
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Expand Up @@ -2524,8 +2524,10 @@
added = '3.13'

[function.Py_TYPE]
# Before 3.14, this was a macro that accessed the PyObject member
added = '3.14'
[function.Py_REFCNT]
# Before 3.14, this was a macro that accessed the PyObject member
added = '3.14'
[function.PyIter_NextItem]
added = '3.14'
Expand Down Expand Up @@ -2641,3 +2643,12 @@
added = '3.15'
[function.PyDict_SetDefaultRef]
added = '3.15'
[function.Py_SIZE]
# Before 3.15, this was a macro that accessed the PyObject member
added = '3.15'
[function.Py_IS_TYPE]
# Before 3.15, this was a macro that accessed the PyObject member
added = '3.15'
[function.Py_SET_SIZE]
# Before 3.15, this was a macro that accessed the PyObject member
added = '3.15'
31 changes: 13 additions & 18 deletions Objects/object.c
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Expand Up @@ -3361,24 +3361,6 @@ Py_GetConstantBorrowed(unsigned int constant_id)
return Py_GetConstant(constant_id);
}


// Py_TYPE() implementation for the stable ABI
#undef Py_TYPE
PyTypeObject*
Py_TYPE(PyObject *ob)
{
return _Py_TYPE(ob);
}


// Py_REFCNT() implementation for the stable ABI
#undef Py_REFCNT
Py_ssize_t
Py_REFCNT(PyObject *ob)
{
return _Py_REFCNT(ob);
}

int
PyUnstable_IsImmortal(PyObject *op)
{
Expand All @@ -3405,3 +3387,16 @@ _PyObject_VisitType(PyObject *op, visitproc visit, void *arg)
Py_VISIT(tp);
return 0;
}

// Implementations for the stable ABI
// Keep these at the end.
#undef Py_TYPE
#undef Py_REFCNT
#undef Py_SIZE
#undef Py_IS_TYPE
#undef Py_SET_SIZE
PyTypeObject* Py_TYPE(PyObject *ob) { return _Py_TYPE_impl(ob); }
Py_ssize_t Py_REFCNT(PyObject *ob) { return _Py_REFCNT(ob); }
Py_ssize_t Py_SIZE(PyObject *o) { return _Py_SIZE_impl(o); }
int Py_IS_TYPE(PyObject *o, PyTypeObject *t) { return _Py_IS_TYPE_impl(o, t); }
void Py_SET_SIZE(PyVarObject *o, Py_ssize_t s) { _Py_SET_SIZE_impl(o, s); }
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3 changes: 3 additions & 0 deletions PC/python3dll.c
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