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

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

5 files changed, 29 insertions, 23 deletions

diff --git a/Include/internal/pycore_object.h b/Include/internal/pycore_object.h
index 347ab68..a88b626 100644
--- a/Include/internal/pycore_object.h
+++ b/Include/internal/pycore_object.h
@@ -42,7 +42,7 @@ static inline void _PyObject_GC_TRACK_impl(const char *filename, int lineno,
 }
 
 #define _PyObject_GC_TRACK(op) \
-    _PyObject_GC_TRACK_impl(__FILE__, __LINE__, (PyObject *)(op))
+    _PyObject_GC_TRACK_impl(__FILE__, __LINE__, _PyObject_CAST(op))
 
 /* Tell the GC to stop tracking this object.
  *
@@ -70,7 +70,7 @@ static inline void _PyObject_GC_UNTRACK_impl(const char *filename, int lineno,
 }
 
 #define _PyObject_GC_UNTRACK(op) \
-    _PyObject_GC_UNTRACK_impl(__FILE__, __LINE__, (PyObject *)(op))
+    _PyObject_GC_UNTRACK_impl(__FILE__, __LINE__, _PyObject_CAST(op))
 
 #ifdef __cplusplus
 }
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
diff --git a/Include/objimpl.h b/Include/objimpl.h
index c455d4b..1c50d8b 100644
--- a/Include/objimpl.h
+++ b/Include/objimpl.h
@@ -258,7 +258,7 @@ PyAPI_FUNC(Py_ssize_t) _PyGC_CollectIfEnabled(void);
 
 PyAPI_FUNC(PyVarObject *) _PyObject_GC_Resize(PyVarObject *, Py_ssize_t);
 #define PyObject_GC_Resize(type, op, n) \
-                ( (type *) _PyObject_GC_Resize((PyVarObject *)(op), (n)) )
+                ( (type *) _PyObject_GC_Resize(_PyVarObject_CAST(op), (n)) )
 
 
 #ifndef Py_LIMITED_API
@@ -356,7 +356,7 @@ PyAPI_FUNC(void) PyObject_GC_Del(void *);
 #define Py_VISIT(op)                                                    \
     do {                                                                \
         if (op) {                                                       \
-            int vret = visit((PyObject *)(op), arg);                    \
+            int vret = visit(_PyObject_CAST(op), arg);                  \
             if (vret)                                                   \
                 return vret;                                            \
         }                                                               \
diff --git a/Include/odictobject.h b/Include/odictobject.h
index 8378dc4..35aff8a 100644
--- a/Include/odictobject.h
+++ b/Include/odictobject.h
@@ -27,13 +27,13 @@ PyAPI_FUNC(int) PyODict_SetItem(PyObject *od, PyObject *key, PyObject *item);
 PyAPI_FUNC(int) PyODict_DelItem(PyObject *od, PyObject *key);
 
 /* wrappers around PyDict* functions */
-#define PyODict_GetItem(od, key) PyDict_GetItem((PyObject *)od, key)
+#define PyODict_GetItem(od, key) PyDict_GetItem(_PyObject_CAST(od), key)
 #define PyODict_GetItemWithError(od, key) \
-    PyDict_GetItemWithError((PyObject *)od, key)
-#define PyODict_Contains(od, key) PyDict_Contains((PyObject *)od, key)
-#define PyODict_Size(od) PyDict_Size((PyObject *)od)
+    PyDict_GetItemWithError(_PyObject_CAST(od), key)
+#define PyODict_Contains(od, key) PyDict_Contains(_PyObject_CAST(od), key)
+#define PyODict_Size(od) PyDict_Size(_PyObject_CAST(od))
 #define PyODict_GetItemString(od, key) \
-    PyDict_GetItemString((PyObject *)od, key)
+    PyDict_GetItemString(_PyObject_CAST(od), key)
 
 #endif
 
diff --git a/Include/unicodeobject.h b/Include/unicodeobject.h
index 0274de6..ffabf0e 100644
--- a/Include/unicodeobject.h
+++ b/Include/unicodeobject.h
@@ -380,7 +380,7 @@ PyAPI_DATA(PyTypeObject) PyUnicodeIter_Type;
     (assert(PyUnicode_Check(op)),                    \
      (((PyASCIIObject *)(op))->wstr) ?               \
       PyUnicode_WSTR_LENGTH(op) :                    \
-      ((void)PyUnicode_AsUnicode((PyObject *)(op)),  \
+      ((void)PyUnicode_AsUnicode(_PyObject_CAST(op)),\
        assert(((PyASCIIObject *)(op))->wstr),        \
        PyUnicode_WSTR_LENGTH(op)))
     /* Py_DEPRECATED(3.3) */
@@ -397,7 +397,7 @@ PyAPI_DATA(PyTypeObject) PyUnicodeIter_Type;
 #define PyUnicode_AS_UNICODE(op) \
     (assert(PyUnicode_Check(op)), \
      (((PyASCIIObject *)(op))->wstr) ? (((PyASCIIObject *)(op))->wstr) : \
-      PyUnicode_AsUnicode((PyObject *)(op)))
+      PyUnicode_AsUnicode(_PyObject_CAST(op)))
     /* Py_DEPRECATED(3.3) */
 
 #define PyUnicode_AS_DATA(op) \
@@ -549,7 +549,7 @@ enum PyUnicode_Kind {
 #define PyUnicode_READY(op)                        \
     (assert(PyUnicode_Check(op)),                       \
      (PyUnicode_IS_READY(op) ?                          \
-      0 : _PyUnicode_Ready((PyObject *)(op))))
+      0 : _PyUnicode_Ready(_PyObject_CAST(op))))
 
 /* Return a maximum character value which is suitable for creating another
    string based on op.  This is always an approximation but more efficient