gh-124127: Make Py_REFCNT() opaque in limited C API 3.14 (#124128)

Author: vstinner

Doc/data/stable_abi.dat

@@ -650,9 +650,10 @@ 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`.)
+* In the limited C API 3.14 and newer, :c:func:`Py_TYPE` and
+  :c:func:`Py_REFCNT` are now implemented as an opaque function call to hide
+  implementation details.
+  (Contributed by Victor Stinner in :gh:`120600` and :gh:`124127`.)
 
 
 Deprecated

Doc/whatsnew/3.14.rst

@@ -77,21 +77,29 @@ check by comparing the reference count field to the immortality reference count.
 #endif  // Py_GIL_DISABLED
 
 
-static inline Py_ssize_t Py_REFCNT(PyObject *ob) {
-#if !defined(Py_GIL_DISABLED)
-    return ob->ob_refcnt;
+// Py_REFCNT() implementation for the stable ABI
+PyAPI_FUNC(Py_ssize_t) Py_REFCNT(PyObject *ob);
+
+#if defined(Py_LIMITED_API) && Py_LIMITED_API+0 >= 0x030e0000
+    // Stable ABI implements Py_REFCNT() as a function call
+    // on limited C API version 3.14 and newer.
 #else
-    uint32_t local = _Py_atomic_load_uint32_relaxed(&ob->ob_ref_local);
-    if (local == _Py_IMMORTAL_REFCNT_LOCAL) {
-        return _Py_IMMORTAL_REFCNT;
+    static inline Py_ssize_t _Py_REFCNT(PyObject *ob) {
+    #if !defined(Py_GIL_DISABLED)
+        return ob->ob_refcnt;
+    #else
+        uint32_t local = _Py_atomic_load_uint32_relaxed(&ob->ob_ref_local);
+        if (local == _Py_IMMORTAL_REFCNT_LOCAL) {
+            return _Py_IMMORTAL_REFCNT;
+        }
+        Py_ssize_t shared = _Py_atomic_load_ssize_relaxed(&ob->ob_ref_shared);
+        return _Py_STATIC_CAST(Py_ssize_t, local) +
+               Py_ARITHMETIC_RIGHT_SHIFT(Py_ssize_t, shared, _Py_REF_SHARED_SHIFT);
+    #endif
     }
-    Py_ssize_t shared = _Py_atomic_load_ssize_relaxed(&ob->ob_ref_shared);
-    return _Py_STATIC_CAST(Py_ssize_t, local) +
-           Py_ARITHMETIC_RIGHT_SHIFT(Py_ssize_t, shared, _Py_REF_SHARED_SHIFT);
-#endif
-}
-#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 < 0x030b0000
-#  define Py_REFCNT(ob) Py_REFCNT(_PyObject_CAST(ob))
+    #if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 < 0x030b0000
+    #  define Py_REFCNT(ob) _Py_REFCNT(_PyObject_CAST(ob))
+    #endif
 #endif
 
 

Include/refcount.h

@@ -0,0 +1,3 @@
+In the limited C API 3.14 and newer, :c:func:`Py_REFCNT` is now implemented
+as an opaque function call to hide implementation details. Patch by Victor
+Stinner.

Lib/test/test_stable_abi_ctypes.py

@@ -2508,6 +2508,8 @@
 
 [function.Py_TYPE]
     added = '3.14'
+[function.Py_REFCNT]
+    added = '3.14'
 [function.PyIter_NextItem]
     added = '3.14'
 [function.PyLong_FromInt32]

Misc/NEWS.d/next/C_API/2024-09-16-16-21-39.gh-issue-124127.LB8DBU.rst

@@ -3039,7 +3039,17 @@ Py_GetConstantBorrowed(unsigned int constant_id)
 
 // Py_TYPE() implementation for the stable ABI
 #undef Py_TYPE
-PyTypeObject* Py_TYPE(PyObject *ob)
+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);
+}