pythongh-120600: Make Py_TYPE() opaque in limited C API 3.14 (python#120601)

In the limited C API 3.14 and newer, Py_TYPE() is now implemented as
an opaque function call to hide implementation details.

Author: vstinner

Doc/data/stable_abi.dat

@@ -301,6 +301,11 @@ New Features
 Porting to Python 3.14
 ----------------------
 
+* In the limited C API 3.14 and newer, :c:func:`Py_TYPE` is now implemented as
+  an opaque function call to hide implementation details.
+  (Contributed by Victor Stinner in :gh:`120600`.)
+
+
 Deprecated
 ----------
 

Doc/whatsnew/3.14.rst

@@ -244,16 +244,26 @@ _Py_IsOwnedByCurrentThread(PyObject *ob)
 }
 #endif
 
-// bpo-39573: The Py_SET_TYPE() function must be used to set an object type.
-static inline PyTypeObject* Py_TYPE(PyObject *ob) {
-#ifdef Py_GIL_DISABLED
-    return (PyTypeObject *)_Py_atomic_load_ptr_relaxed(&ob->ob_type);
+// Py_TYPE() implementation for the stable ABI
+PyAPI_FUNC(PyTypeObject*) Py_TYPE(PyObject *ob);
+
+#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.
 #else
-    return ob->ob_type;
-#endif
-}
-#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 < 0x030b0000
-#  define Py_TYPE(ob) Py_TYPE(_PyObject_CAST(ob))
+    static inline PyTypeObject* _Py_TYPE(PyObject *ob)
+    {
+    #if defined(Py_GIL_DISABLED)
+        return (PyTypeObject *)_Py_atomic_load_ptr_relaxed(&ob->ob_type);
+    #else
+        return ob->ob_type;
+    #endif
+    }
+    #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
 #endif
 
 PyAPI_DATA(PyTypeObject) PyLong_Type;

Include/object.h

@@ -0,0 +1,2 @@
+In the limited C API 3.14 and newer, :c:func:`Py_TYPE` is now implemented as an
+opaque function call to hide implementation details. Patch by Victor Stinner.

Lib/test/test_stable_abi_ctypes.py

@@ -2507,3 +2507,6 @@
     added = '3.13'
 [function.PyEval_GetFrameLocals]
     added = '3.13'
+
+[function.Py_TYPE]
+    added = '3.14'

Misc/NEWS.d/next/C API/2024-06-16-22-58-47.gh-issue-120600.TJdf0w.rst

@@ -3001,3 +3001,11 @@ Py_GetConstantBorrowed(unsigned int constant_id)
     // All constants are immortal
     return Py_GetConstant(constant_id);
 }
+
+
+// Py_TYPE() implementation for the stable ABI
+#undef Py_TYPE
+PyTypeObject* Py_TYPE(PyObject *ob)
+{
+    return _Py_TYPE(ob);
+}