Use Python 3.11 _Py_CAST() macro (#35)

Remove _Py_StealRef() and _Py_XStealRef() functions.

Author: vstinner

pythoncapi_compat.h

@@ -33,17 +33,23 @@ extern "C" {
 
 
 // C++ compatibility
+#ifndef _Py_CAST
+#  ifdef __cplusplus
+#    define _Py_CAST(type, expr) \
+         const_cast<type>(reinterpret_cast<const type>(expr))
+#  else
+#    define _Py_CAST(type, expr) ((type)(expr))
+#  endif
+#endif
 #ifdef __cplusplus
-#  define PYCAPI_COMPAT_CAST(TYPE, EXPR) reinterpret_cast<TYPE>(EXPR)
 #  define PYCAPI_COMPAT_NULL nullptr
 #else
-#  define PYCAPI_COMPAT_CAST(TYPE, EXPR) ((TYPE)(EXPR))
 #  define PYCAPI_COMPAT_NULL NULL
 #endif
 
 // Cast argument to PyObject* type.
 #ifndef _PyObject_CAST
-#  define _PyObject_CAST(op) PYCAPI_COMPAT_CAST(PyObject*, op)
+#  define _PyObject_CAST(op) _Py_CAST(PyObject*, op)
 #endif
 
 
@@ -71,30 +77,6 @@ _Py_XNewRef(PyObject *obj)
 #endif
 
 
-// See https://bugs.python.org/issue42522
-#if !defined(_Py_StealRef)
-PYCAPI_COMPAT_STATIC_INLINE(PyObject*)
-__Py_StealRef(PyObject *obj)
-{
-    Py_DECREF(obj);
-    return obj;
-}
-#define _Py_StealRef(obj) __Py_StealRef(_PyObject_CAST(obj))
-#endif
-
-
-// See https://bugs.python.org/issue42522
-#if !defined(_Py_XStealRef)
-PYCAPI_COMPAT_STATIC_INLINE(PyObject*)
-__Py_XStealRef(PyObject *obj)
-{
-    Py_XDECREF(obj);
-    return obj;
-}
-#define _Py_XStealRef(obj) __Py_XStealRef(_PyObject_CAST(obj))
-#endif
-
-
 // bpo-39573 added Py_SET_REFCNT() to Python 3.9.0a4
 #if PY_VERSION_HEX < 0x030900A4 && !defined(Py_SET_REFCNT)
 PYCAPI_COMPAT_STATIC_INLINE(void)
@@ -170,15 +152,16 @@ PyFrame_GetCode(PyFrameObject *frame)
 {
     assert(frame != PYCAPI_COMPAT_NULL);
     assert(frame->f_code != PYCAPI_COMPAT_NULL);
-    return PYCAPI_COMPAT_CAST(PyCodeObject*, Py_NewRef(frame->f_code));
+    return _Py_CAST(PyCodeObject*, Py_NewRef(frame->f_code));
 }
 #endif
 
 PYCAPI_COMPAT_STATIC_INLINE(PyCodeObject*)
 _PyFrame_GetCodeBorrow(PyFrameObject *frame)
 {
-    return PYCAPI_COMPAT_CAST(PyCodeObject *,
-                              _Py_StealRef(PyFrame_GetCode(frame)));
+    PyCodeObject *code = PyFrame_GetCode(frame);
+    Py_DECREF(code);
+    return code;
 }
 
 
@@ -188,16 +171,17 @@ PYCAPI_COMPAT_STATIC_INLINE(PyFrameObject*)
 PyFrame_GetBack(PyFrameObject *frame)
 {
     assert(frame != PYCAPI_COMPAT_NULL);
-    return PYCAPI_COMPAT_CAST(PyFrameObject*, Py_XNewRef(frame->f_back));
+    return _Py_CAST(PyFrameObject*, Py_XNewRef(frame->f_back));
 }
 #endif
 
 #if !defined(PYPY_VERSION)
 PYCAPI_COMPAT_STATIC_INLINE(PyFrameObject*)
 _PyFrame_GetBackBorrow(PyFrameObject *frame)
 {
-    return PYCAPI_COMPAT_CAST(PyFrameObject *,
-                              _Py_XStealRef(PyFrame_GetBack(frame)));
+    PyFrameObject *back = PyFrame_GetBack(frame);
+    Py_XDECREF(back);
+    return back;
 }
 #endif
 
@@ -276,16 +260,17 @@ PYCAPI_COMPAT_STATIC_INLINE(PyFrameObject*)
 PyThreadState_GetFrame(PyThreadState *tstate)
 {
     assert(tstate != PYCAPI_COMPAT_NULL);
-    return PYCAPI_COMPAT_CAST(PyFrameObject *, Py_XNewRef(tstate->frame));
+    return _Py_CAST(PyFrameObject *, Py_XNewRef(tstate->frame));
 }
 #endif
 
 #if !defined(PYPY_VERSION)
 PYCAPI_COMPAT_STATIC_INLINE(PyFrameObject*)
 _PyThreadState_GetFrameBorrow(PyThreadState *tstate)
 {
-    return PYCAPI_COMPAT_CAST(PyFrameObject*,
-                              _Py_XStealRef(PyThreadState_GetFrame(tstate)));
+    PyFrameObject *frame = PyThreadState_GetFrame(tstate);
+    Py_XDECREF(frame);
+    return frame;
 }
 #endif
 
@@ -429,7 +414,7 @@ PyObject_GC_IsTracked(PyObject* obj)
 PYCAPI_COMPAT_STATIC_INLINE(int)
 PyObject_GC_IsFinalized(PyObject *obj)
 {
-    PyGC_Head *gc = PYCAPI_COMPAT_CAST(PyGC_Head *, obj) - 1;
+    PyGC_Head *gc = _Py_CAST(PyGC_Head*, obj) - 1;
     return (PyObject_IS_GC(obj) && _PyGCHead_FINALIZED(gc));
 }
 #endif

tests/test_pythoncapi_compat_cext.c

@@ -130,35 +130,6 @@ test_py_is(PyObject *Py_UNUSED(module), PyObject* Py_UNUSED(ignored))
 }
 
 
-static PyObject *
-test_steal_ref(PyObject *Py_UNUSED(module), PyObject* Py_UNUSED(ignored))
-{
-    PyObject *obj = PyList_New(0);
-    if (obj == NULL) {
-        return NULL;
-    }
-    Py_ssize_t refcnt = Py_REFCNT(obj);
-
-    // _Py_StealRef()
-    Py_INCREF(obj);
-    PyObject *ref = _Py_StealRef(obj);
-    assert(ref == obj);
-    assert(Py_REFCNT(obj) == refcnt);
-
-    // _Py_XStealRef()
-    Py_INCREF(obj);
-    PyObject *xref = _Py_XStealRef(obj);
-    assert(xref == obj);
-    assert(Py_REFCNT(obj) == refcnt);
-
-    assert(_Py_XStealRef(NULL) == NULL);
-
-    assert(Py_REFCNT(obj) == refcnt);
-    Py_DECREF(obj);
-    Py_RETURN_NONE;
-}
-
-
 #if !defined(PYPY_VERSION)
 static PyObject *
 test_frame(PyObject *Py_UNUSED(module), PyObject* Py_UNUSED(ignored))
@@ -516,7 +487,6 @@ test_code(PyObject *Py_UNUSED(module), PyObject* Py_UNUSED(ignored))
 static struct PyMethodDef methods[] = {
     {"test_object", test_object, METH_NOARGS, NULL},
     {"test_py_is", test_py_is, METH_NOARGS, NULL},
-    {"test_steal_ref", test_steal_ref, METH_NOARGS, NULL},
 #if !defined(PYPY_VERSION)
     {"test_frame", test_frame, METH_NOARGS, NULL},
 #endif