[3.11] Revert "[3.11] gh-98724: Fix Py_CLEAR() macro side effects (#99100)" (#99573)

Revert "gh-98724: Fix Py_CLEAR() macro side effects (#99100) (#99288)"

This reverts commit 108289085719db8b227d65ce945e806f91be8f80.

diff --git a/Include/cpython/object.h b/Include/cpython/object.h
index 0d0f1e23673e58b518e4bc5b9387c01b8ac95a4d..b018dabf9d862ff501eae15a8d0e0e58fba4697a 100644 (file)
--- a/Include/cpython/object.h
+++ b/Include/cpython/object.h
@@ -309,41 +309,37 @@ _PyObject_GenericSetAttrWithDict(PyObject *, PyObject *,
 
 PyAPI_FUNC(PyObject *) _PyObject_FunctionStr(PyObject *);
 
-/* Safely decref `dst` and set `dst` to `src`.
+/* Safely decref `op` and set `op` to `op2`.
  *
  * As in case of Py_CLEAR "the obvious" code can be deadly:
  *
- *     Py_DECREF(dst);
- *     dst = src;
+ *     Py_DECREF(op);
+ *     op = op2;
  *
  * The safe way is:
  *
- *      Py_SETREF(dst, src);
+ *      Py_SETREF(op, op2);
  *
- * That arranges to set `dst` to `src` _before_ decref'ing, so that any code
- * triggered as a side-effect of `dst` getting torn down no longer believes
- * `dst` points to a valid object.
+ * That arranges to set `op` to `op2` _before_ decref'ing, so that any code
+ * triggered as a side-effect of `op` getting torn down no longer believes
+ * `op` points to a valid object.
  *
- * gh-98724: Use the _tmp_dst_ptr variable to evaluate the 'dst' macro argument
- * exactly once, to prevent the duplication of side effects in this macro.
+ * Py_XSETREF is a variant of Py_SETREF that uses Py_XDECREF instead of
+ * Py_DECREF.
  */
-#define Py_SETREF(dst, src)                                     \
-    do {                                                        \
-        PyObject **_tmp_dst_ptr = _Py_CAST(PyObject**, &(dst)); \
-        PyObject *_tmp_dst = (*_tmp_dst_ptr);                   \
-        *_tmp_dst_ptr = _PyObject_CAST(src);                    \
-        Py_DECREF(_tmp_dst);                                    \
+
+#define Py_SETREF(op, op2)                      \
+    do {                                        \
+        PyObject *_py_tmp = _PyObject_CAST(op); \
+        (op) = (op2);                           \
+        Py_DECREF(_py_tmp);                     \
     } while (0)
 
-/* Py_XSETREF() is a variant of Py_SETREF() that uses Py_XDECREF() instead of
- * Py_DECREF().
- */
-#define Py_XSETREF(dst, src)                                    \
-    do {                                                        \
-        PyObject **_tmp_dst_ptr = _Py_CAST(PyObject**, &(dst)); \
-        PyObject *_tmp_dst = (*_tmp_dst_ptr);                   \
-        *_tmp_dst_ptr = _PyObject_CAST(src);                    \
-        Py_XDECREF(_tmp_dst);                                   \
+#define Py_XSETREF(op, op2)                     \
+    do {                                        \
+        PyObject *_py_tmp = _PyObject_CAST(op); \
+        (op) = (op2);                           \
+        Py_XDECREF(_py_tmp);                    \
     } while (0)
 
 

diff --git a/Include/object.h b/Include/object.h
index 73bebcde993cbf7b055fee5bb95fd87529c420fa..f2af428e2bb9730e4dd0e610d21b44c7610d3d2f 100644 (file)
--- a/Include/object.h
+++ b/Include/object.h
@@ -575,21 +575,16 @@ static inline void Py_DECREF(PyObject *op)
  * one of those can't cause problems -- but in part that relies on that
  * Python integers aren't currently weakly referencable.  Best practice is
  * to use Py_CLEAR() even if you can't think of a reason for why you need to.
- *
- * gh-98724: Use the _py_tmp_ptr variable to evaluate the macro argument
- * exactly once, to prevent the duplication of side effects in this macro.
  */
-#define Py_CLEAR(op)                                          \
-    do {                                                      \
-        PyObject **_py_tmp_ptr = _Py_CAST(PyObject**, &(op)); \
-        if (*_py_tmp_ptr != NULL) {                           \
-            PyObject* _py_tmp = (*_py_tmp_ptr);               \
-            *_py_tmp_ptr = NULL;                              \
-            Py_DECREF(_py_tmp);                               \
-        }                                                     \
+#define Py_CLEAR(op)                            \
+    do {                                        \
+        PyObject *_py_tmp = _PyObject_CAST(op); \
+        if (_py_tmp != NULL) {                  \
+            (op) = NULL;                        \
+            Py_DECREF(_py_tmp);                 \
+        }                                       \
     } while (0)
 
-
 /* Function to use in case the object pointer can be NULL: */
 static inline void Py_XINCREF(PyObject *op)
 {

diff --git a/Misc/NEWS.d/next/C API/2022-11-04-16-13-35.gh-issue-98724.p0urWO.rst b/Misc/NEWS.d/next/C API/2022-11-04-16-13-35.gh-issue-98724.p0urWO.rst
deleted file mode 100644 (file)
index 2613b17..0000000
--- a/Misc/NEWS.d/next/C API/2022-11-04-16-13-35.gh-issue-98724.p0urWO.rst
+++ /dev/null
@@ -1,3 +0,0 @@
-The :c:macro:`Py_CLEAR`, :c:macro:`Py_SETREF` and :c:macro:`Py_XSETREF` macros
-now only evaluate their argument once. If the argument has side effects, these
-side effects are no longer duplicated. Patch by Victor Stinner.

diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index 92a2a07e2a44c876b354c002b9986b5e7e74bb27..1291eff481cbb85c2d3f6160770d6a04dd5b6e9f 100644 (file)
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -5684,91 +5684,6 @@ test_set_type_size(PyObject *self, PyObject *Py_UNUSED(ignored))
 }
 
 
-// Test Py_CLEAR() macro
-static PyObject*
-test_py_clear(PyObject *self, PyObject *Py_UNUSED(ignored))
-{
-    // simple case with a variable
-    PyObject *obj = PyList_New(0);
-    if (obj == NULL) {
-        return NULL;
-    }
-    Py_CLEAR(obj);
-    assert(obj == NULL);
-
-    // gh-98724: complex case, Py_CLEAR() argument has a side effect
-    PyObject* array[1];
-    array[0] = PyList_New(0);
-    if (array[0] == NULL) {
-        return NULL;
-    }
-
-    PyObject **p = array;
-    Py_CLEAR(*p++);
-    assert(array[0] == NULL);
-    assert(p == array + 1);
-
-    Py_RETURN_NONE;
-}
-
-
-// Test Py_SETREF() and Py_XSETREF() macros, similar to test_py_clear()
-static PyObject*
-test_py_setref(PyObject *self, PyObject *Py_UNUSED(ignored))
-{
-    // Py_SETREF() simple case with a variable
-    PyObject *obj = PyList_New(0);
-    if (obj == NULL) {
-        return NULL;
-    }
-    Py_SETREF(obj, NULL);
-    assert(obj == NULL);
-
-    // Py_XSETREF() simple case with a variable
-    PyObject *obj2 = PyList_New(0);
-    if (obj2 == NULL) {
-        return NULL;
-    }
-    Py_XSETREF(obj2, NULL);
-    assert(obj2 == NULL);
-    // test Py_XSETREF() when the argument is NULL
-    Py_XSETREF(obj2, NULL);
-    assert(obj2 == NULL);
-
-    // gh-98724: complex case, Py_SETREF() argument has a side effect
-    PyObject* array[1];
-    array[0] = PyList_New(0);
-    if (array[0] == NULL) {
-        return NULL;
-    }
-
-    PyObject **p = array;
-    Py_SETREF(*p++, NULL);
-    assert(array[0] == NULL);
-    assert(p == array + 1);
-
-    // gh-98724: complex case, Py_XSETREF() argument has a side effect
-    PyObject* array2[1];
-    array2[0] = PyList_New(0);
-    if (array2[0] == NULL) {
-        return NULL;
-    }
-
-    PyObject **p2 = array2;
-    Py_XSETREF(*p2++, NULL);
-    assert(array2[0] == NULL);
-    assert(p2 == array2 + 1);
-
-    // test Py_XSETREF() when the argument is NULL
-    p2 = array2;
-    Py_XSETREF(*p2++, NULL);
-    assert(array2[0] == NULL);
-    assert(p2 == array2 + 1);
-
-    Py_RETURN_NONE;
-}
-
-
 #define TEST_REFCOUNT() \
     do { \
         PyObject *obj = PyList_New(0); \
@@ -6560,8 +6475,6 @@ static PyMethodDef TestMethods[] = {
     {"pynumber_tobase", pynumber_tobase, METH_VARARGS},
     {"without_gc", without_gc, METH_O},
     {"test_set_type_size", test_set_type_size, METH_NOARGS},
-    {"test_py_clear", test_py_clear, METH_NOARGS},
-    {"test_py_setref", test_py_setref, METH_NOARGS},
     {"test_refcount_macros", test_refcount_macros, METH_NOARGS},
     {"test_refcount_funcs", test_refcount_funcs, METH_NOARGS},
     {"test_py_is_macros", test_py_is_macros, METH_NOARGS},