bpo-35059: Add _PyObject_CAST() macro (GH-10645)

Add _PyObject_CAST() and _PyVarObject_CAST() macros to cast argument
to PyObject* and PyVarObject* properly.

1 files changed, 17 insertions, 11 deletions

diff --git a/Include/object.h b/Include/object.h
index 5947b79..cdcdca8 100644
--- a/Include/object.h
+++ b/Include/object.h
@@ -112,14 +112,20 @@ typedef struct _object {
     struct _typeobject *ob_type;
 } PyObject;
 
+/* Cast argument to PyObject* type. */
+#define _PyObject_CAST(op) ((PyObject*)(op))
+
 typedef struct {
     PyObject ob_base;
     Py_ssize_t ob_size; /* Number of items in variable part */
 } PyVarObject;
 
-#define Py_REFCNT(ob)           (((PyObject*)(ob))->ob_refcnt)
-#define Py_TYPE(ob)             (((PyObject*)(ob))->ob_type)
-#define Py_SIZE(ob)             (((PyVarObject*)(ob))->ob_size)
+/* Cast argument to PyVarObject* type. */
+#define _PyVarObject_CAST(op) ((PyVarObject*)(op))
+
+#define Py_REFCNT(ob)           (_PyObject_CAST(ob)->ob_refcnt)
+#define Py_TYPE(ob)             (_PyObject_CAST(ob)->ob_type)
+#define Py_SIZE(ob)             (_PyVarObject_CAST(ob)->ob_size)
 
 #ifndef Py_LIMITED_API
 /********************* String Literals ****************************************/
@@ -814,7 +820,7 @@ static inline void _Py_INCREF(PyObject *op)
     op->ob_refcnt++;
 }
 
-#define Py_INCREF(op) _Py_INCREF((PyObject *)(op))
+#define Py_INCREF(op) _Py_INCREF(_PyObject_CAST(op))
 
 static inline void _Py_DECREF(const char *filename, int lineno,
                               PyObject *op)
@@ -832,7 +838,7 @@ static inline void _Py_DECREF(const char *filename, int lineno,
     }
 }
 
-#define Py_DECREF(op) _Py_DECREF(__FILE__, __LINE__, (PyObject *)(op))
+#define Py_DECREF(op) _Py_DECREF(__FILE__, __LINE__, _PyObject_CAST(op))
 
 
 /* Safely decref `op` and set `op` to NULL, especially useful in tp_clear
@@ -871,7 +877,7 @@ static inline void _Py_DECREF(const char *filename, int lineno,
  */
 #define Py_CLEAR(op)                            \
     do {                                        \
-        PyObject *_py_tmp = (PyObject *)(op);   \
+        PyObject *_py_tmp = _PyObject_CAST(op); \
         if (_py_tmp != NULL) {                  \
             (op) = NULL;                        \
             Py_DECREF(_py_tmp);                 \
@@ -886,7 +892,7 @@ static inline void _Py_XINCREF(PyObject *op)
     }
 }
 
-#define Py_XINCREF(op) _Py_XINCREF((PyObject *)(op))
+#define Py_XINCREF(op) _Py_XINCREF(_PyObject_CAST(op))
 
 static inline void _Py_XDECREF(PyObject *op)
 {
@@ -895,7 +901,7 @@ static inline void _Py_XDECREF(PyObject *op)
     }
 }
 
-#define Py_XDECREF(op) _Py_XDECREF((PyObject *)(op))
+#define Py_XDECREF(op) _Py_XDECREF(_PyObject_CAST(op))
 
 #ifndef Py_LIMITED_API
 /* Safely decref `op` and set `op` to `op2`.
@@ -919,14 +925,14 @@ static inline void _Py_XDECREF(PyObject *op)
 
 #define Py_SETREF(op, op2)                      \
     do {                                        \
-        PyObject *_py_tmp = (PyObject *)(op);   \
+        PyObject *_py_tmp = _PyObject_CAST(op); \
         (op) = (op2);                           \
         Py_DECREF(_py_tmp);                     \
     } while (0)
 
 #define Py_XSETREF(op, op2)                     \
     do {                                        \
-        PyObject *_py_tmp = (PyObject *)(op);   \
+        PyObject *_py_tmp = _PyObject_CAST(op); \
         (op) = (op2);                           \
         Py_XDECREF(_py_tmp);                    \
     } while (0)
@@ -1122,7 +1128,7 @@ PyAPI_FUNC(void) _PyTrash_thread_destroy_chain(void);
                 _PyTrash_thread_destroy_chain(); \
         } \
         else \
-            _PyTrash_thread_deposit_object((PyObject*)op); \
+            _PyTrash_thread_deposit_object(_PyObject_CAST(op)); \
     } while (0);
 
 #ifndef Py_LIMITED_API