gh-115754: Get singletons by function calls in lmited C API 3.13

In the limited C API version 3.13, getting Py_None, Py_False,
Py_True, Py_Ellipsis and Py_NotImplemented singletons is now
implemented as function calls at the stable ABI level to hide
implementation details. Getting these constants still return borrowed
references.

Author: vstinner

Doc/whatsnew/3.13.rst

@@ -1645,6 +1645,11 @@ New Features
   between native integer types and Python :class:`int` objects.
   (Contributed by Steve Dower in :gh:`111140`.)
 
+* In the limited C API version 3.13, getting ``Py_None``, ``Py_False``,
+  ``Py_True``, ``Py_Ellipsis`` and ``Py_NotImplemented`` singletons is now
+  implemented as function calls at the stable ABI level to hide implementation
+  details. Getting these constants still return borrowed references.
+  (Contributed by Victor Stinner in :gh:`115754`.)
 
 Porting to Python 3.13
 ----------------------

Include/boolobject.h

@@ -16,10 +16,17 @@ extern "C" {
 /* Don't use these directly */
 PyAPI_DATA(PyLongObject) _Py_FalseStruct;
 PyAPI_DATA(PyLongObject) _Py_TrueStruct;
+PyAPI_FUNC(PyObject*) _Py_GetFalse(void);
+PyAPI_FUNC(PyObject*) _Py_GetTrue(void);
+
+#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x030D0000
+#  define Py_False _Py_GetFalse()
+#  define Py_True _Py_GetTrue()
+#else
+#  define Py_False _PyObject_CAST(&_Py_FalseStruct)
+#  define Py_True _PyObject_CAST(&_Py_TrueStruct)
+#endif
 
-/* Use these macros */
-#define Py_False _PyObject_CAST(&_Py_FalseStruct)
-#define Py_True _PyObject_CAST(&_Py_TrueStruct)
 
 // Test if an object is the True singleton, the same as "x is True" in Python.
 PyAPI_FUNC(int) Py_IsTrue(PyObject *x);

Include/object.h

@@ -1070,7 +1070,13 @@ _Py_NoneStruct is an object of undefined type which can be used in contexts
 where NULL (nil) is not suitable (since NULL often means 'error').
 */
 PyAPI_DATA(PyObject) _Py_NoneStruct; /* Don't use this directly */
-#define Py_None (&_Py_NoneStruct)
+PyAPI_FUNC(PyObject*) _Py_GetNone(void);
+
+#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x030D0000
+#  define Py_None _Py_GetNone()
+#else
+#  define Py_None (&_Py_NoneStruct)
+#endif
 
 // Test if an object is the None singleton, the same as "x is None" in Python.
 PyAPI_FUNC(int) Py_IsNone(PyObject *x);
@@ -1084,7 +1090,13 @@ Py_NotImplemented is a singleton used to signal that an operation is
 not implemented for a given type combination.
 */
 PyAPI_DATA(PyObject) _Py_NotImplementedStruct; /* Don't use this directly */
-#define Py_NotImplemented (&_Py_NotImplementedStruct)
+PyAPI_FUNC(PyObject*) _Py_GetNotImplemented(void);
+
+#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x030D0000
+#  define Py_NotImplemented _Py_GetNotImplemented()
+#else
+#  define Py_NotImplemented (&_Py_NotImplementedStruct)
+#endif
 
 /* Macro for returning Py_NotImplemented from a function */
 #define Py_RETURN_NOTIMPLEMENTED return Py_NotImplemented

Include/sliceobject.h

@@ -7,8 +7,13 @@ extern "C" {
 /* The unique ellipsis object "..." */
 
 PyAPI_DATA(PyObject) _Py_EllipsisObject; /* Don't use this directly */
+PyAPI_FUNC(PyObject*) _Py_GetEllipsis(void);
 
-#define Py_Ellipsis (&_Py_EllipsisObject)
+#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x030D0000
+#  define Py_Ellipsis _Py_GetEllipsis()
+#else
+#  define Py_Ellipsis (&_Py_EllipsisObject)
+#endif
 
 /* Slice object interface */
 

Misc/NEWS.d/next/C API/2024-03-11-09-24-35.gh-issue-115754.zLdv82.rst

@@ -0,0 +1,5 @@
+In the limited C API version 3.13, getting ``Py_None``, ``Py_False``,
+``Py_True``, ``Py_Ellipsis`` and ``Py_NotImplemented`` singletons is now
+implemented as function calls at the stable ABI level to hide implementation
+details. Getting these constants still return borrowed references. Patch by
+Victor Stinner.

Misc/stable_abi.toml

@@ -2496,3 +2496,13 @@
 [typedef.PyCFunctionFastWithKeywords]
     added = '3.13'
     # "abi-only" since 3.10.  (Same story as PyCFunctionFast.)
+[typedef._Py_GetNone]
+    added = '3.13'
+[typedef._Py_GetFalse]
+    added = '3.13'
+[typedef._Py_GetTrue]
+    added = '3.13'
+[typedef._Py_GetEllipsis]
+    added = '3.13'
+[typedef._Py_GetNotImplemented]
+    added = '3.13'

Objects/longobject.c

@@ -6592,16 +6592,23 @@ _PyLong_FiniTypes(PyInterpreterState *interp)
     _PyStructSequence_FiniBuiltin(interp, &Int_InfoType);
 }
 
-#undef PyUnstable_Long_IsCompact
 
+// -- Stable ABI ------------------------------------------------------------
+
+#undef PyUnstable_Long_IsCompact
 int
 PyUnstable_Long_IsCompact(const PyLongObject* op) {
     return _PyLong_IsCompact(op);
 }
 
 #undef PyUnstable_Long_CompactValue
-
 Py_ssize_t
 PyUnstable_Long_CompactValue(const PyLongObject* op) {
     return _PyLong_CompactValue(op);
 }
+
+PyObject* _Py_GetFalse(void)
+{ return _PyObject_CAST(&_Py_FalseStruct); }
+
+PyObject* _Py_GetTrue(void)
+{ return _PyObject_CAST(&_Py_TrueStruct); }

Objects/object.c

@@ -2920,6 +2920,8 @@ PyObject_GET_WEAKREFS_LISTPTR(PyObject *op)
 }
 
 
+// -- Stable ABI ------------------------------------------------------------
+
 #undef Py_NewRef
 #undef Py_XNewRef
 
@@ -2970,3 +2972,9 @@ _Py_SetRefcnt(PyObject *ob, Py_ssize_t refcnt)
 {
     Py_SET_REFCNT(ob, refcnt);
 }
+
+PyObject* _Py_GetNone(void)
+{ return &_Py_NoneStruct; }
+
+PyObject* _Py_GetNotImplemented(void)
+{ return &_Py_NotImplementedStruct; }

Objects/sliceobject.c

@@ -721,3 +721,9 @@ PyTypeObject PySlice_Type = {
     0,                                          /* tp_alloc */
     slice_new,                                  /* tp_new */
 };
+
+
+// -- Stable ABI ------------------------------------------------------------
+
+PyObject* _Py_GetEllipsis(void)
+{ return &_Py_EllipsisObject; }