gh-91768: C API no longer use "const PyObject*" type (#91769)

Py_REFCNT(), Py_TYPE(), Py_SIZE() and Py_IS_TYPE() functions argument
type is now "PyObject*", rather than "const PyObject*".

* Replace also "const PyObject*" with "PyObject*" in functions:

  * _Py_strhex_impl()
  * _Py_strhex_with_sep()
  * _Py_strhex_bytes_with_sep()

* Remove _PyObject_CAST_CONST() and _PyVarObject_CAST_CONST() macros.
* Py_IS_TYPE() can now use Py_TYPE() in its implementation.

Doc/c-api/structures.rst

@@ -62,14 +62,14 @@ the definition of all other Python objects.
    See documentation of :c:type:`PyVarObject` above.
 
 
-.. c:function:: int Py_Is(const PyObject *x, const PyObject *y)
+.. c:function:: int Py_Is(PyObject *x, PyObject *y)
 
    Test if the *x* object is the *y* object, the same as ``x is y`` in Python.
 
    .. versionadded:: 3.10
 
 
-.. c:function:: int Py_IsNone(const PyObject *x)
+.. c:function:: int Py_IsNone(PyObject *x)
 
    Test if an object is the ``None`` singleton,
    the same as ``x is None`` in Python.
@@ -77,7 +77,7 @@ the definition of all other Python objects.
    .. versionadded:: 3.10
 
 
-.. c:function:: int Py_IsTrue(const PyObject *x)
+.. c:function:: int Py_IsTrue(PyObject *x)
 
    Test if an object is the ``True`` singleton,
    the same as ``x is True`` in Python.
@@ -85,7 +85,7 @@ the definition of all other Python objects.
    .. versionadded:: 3.10
 
 
-.. c:function:: int Py_IsFalse(const PyObject *x)
+.. c:function:: int Py_IsFalse(PyObject *x)
 
    Test if an object is the ``False`` singleton,
    the same as ``x is False`` in Python.
@@ -93,7 +93,7 @@ the definition of all other Python objects.
    .. versionadded:: 3.10
 
 
-.. c:function:: PyTypeObject* Py_TYPE(const PyObject *o)
+.. c:function:: PyTypeObject* Py_TYPE(PyObject *o)
 
    Get the type of the Python object *o*.
 
@@ -103,6 +103,7 @@ the definition of all other Python objects.
 
    .. versionchanged:: 3.11
       :c:func:`Py_TYPE()` is changed to an inline static function.
+      The parameter type is no longer :c:type:`const PyObject*`.
 
 
 .. c:function:: int Py_IS_TYPE(PyObject *o, PyTypeObject *type)
@@ -120,12 +121,15 @@ the definition of all other Python objects.
    .. versionadded:: 3.9
 
 
-.. c:function:: Py_ssize_t Py_REFCNT(const PyObject *o)
+.. c:function:: Py_ssize_t Py_REFCNT(PyObject *o)
 
    Get the reference count of the Python object *o*.
 
    Use the :c:func:`Py_SET_REFCNT()` function to set an object reference count.
 
+   .. versionchanged:: 3.11
+      The parameter type is no longer :c:type:`const PyObject*`.
+
    .. versionchanged:: 3.10
       :c:func:`Py_REFCNT()` is changed to the inline static function.
 
@@ -137,7 +141,7 @@ the definition of all other Python objects.
    .. versionadded:: 3.9
 
 
-.. c:function:: Py_ssize_t Py_SIZE(const PyVarObject *o)
+.. c:function:: Py_ssize_t Py_SIZE(PyVarObject *o)
 
    Get the size of the Python object *o*.
 
@@ -145,6 +149,7 @@ the definition of all other Python objects.
 
    .. versionchanged:: 3.11
       :c:func:`Py_SIZE()` is changed to an inline static function.
+      The parameter type is no longer :c:type:`const PyVarObject*`.
 
 
 .. c:function:: void Py_SET_SIZE(PyVarObject *o, Py_ssize_t size)

Include/internal/pycore_strhex.h

@@ -22,12 +22,12 @@ PyAPI_FUNC(PyObject*) _Py_strhex_bytes(
 PyAPI_FUNC(PyObject*) _Py_strhex_with_sep(
     const char* argbuf,
     const Py_ssize_t arglen,
-    const PyObject* sep,
+    PyObject* sep,
     const int bytes_per_group);
 PyAPI_FUNC(PyObject*) _Py_strhex_bytes_with_sep(
     const char* argbuf,
     const Py_ssize_t arglen,
-    const PyObject* sep,
+    PyObject* sep,
     const int bytes_per_group);
 
 #ifdef __cplusplus

Include/object.h

@@ -105,7 +105,6 @@ struct _object {
 
 /* Cast argument to PyObject* type. */
 #define _PyObject_CAST(op) ((PyObject*)(op))
-#define _PyObject_CAST_CONST(op) ((const PyObject*)(op))
 
 typedef struct {
     PyObject ob_base;
@@ -114,7 +113,6 @@ typedef struct {
 
 /* Cast argument to PyVarObject* type. */
 #define _PyVarObject_CAST(op) ((PyVarObject*)(op))
-#define _PyVarObject_CAST_CONST(op) ((const PyVarObject*)(op))
 
 
 // Test if the 'x' object is the 'y' object, the same as "x is y" in Python.
@@ -122,31 +120,29 @@ PyAPI_FUNC(int) Py_Is(PyObject *x, PyObject *y);
 #define Py_Is(x, y) ((x) == (y))
 
 
-static inline Py_ssize_t Py_REFCNT(const PyObject *ob) {
+static inline Py_ssize_t Py_REFCNT(PyObject *ob) {
     return ob->ob_refcnt;
 }
-#define Py_REFCNT(ob) Py_REFCNT(_PyObject_CAST_CONST(ob))
+#define Py_REFCNT(ob) Py_REFCNT(_PyObject_CAST(ob))
 
 
 // bpo-39573: The Py_SET_TYPE() function must be used to set an object type.
-static inline PyTypeObject* Py_TYPE(const PyObject *ob) {
+static inline PyTypeObject* Py_TYPE(PyObject *ob) {
     return ob->ob_type;
 }
-#define Py_TYPE(ob) Py_TYPE(_PyObject_CAST_CONST(ob))
+#define Py_TYPE(ob) Py_TYPE(_PyObject_CAST(ob))
 
 // bpo-39573: The Py_SET_SIZE() function must be used to set an object size.
-static inline Py_ssize_t Py_SIZE(const PyVarObject *ob) {
+static inline Py_ssize_t Py_SIZE(PyVarObject *ob) {
     return ob->ob_size;
 }
-#define Py_SIZE(ob) Py_SIZE(_PyVarObject_CAST_CONST(ob))
+#define Py_SIZE(ob) Py_SIZE(_PyVarObject_CAST(ob))
 
 
-static inline int Py_IS_TYPE(const PyObject *ob, const PyTypeObject *type) {
-    // bpo-44378: Don't use Py_TYPE() since Py_TYPE() requires a non-const
-    // object.
-    return ob->ob_type == type;
+static inline int Py_IS_TYPE(PyObject *ob, PyTypeObject *type) {
+    return Py_TYPE(ob) == type;
 }
-#define Py_IS_TYPE(ob, type) Py_IS_TYPE(_PyObject_CAST_CONST(ob), type)
+#define Py_IS_TYPE(ob, type) Py_IS_TYPE(_PyObject_CAST(ob), type)
 
 
 static inline void Py_SET_REFCNT(PyObject *ob, Py_ssize_t refcnt) {

Misc/NEWS.d/next/C API/2022-04-21-01-48-22.gh-issue-91768.x_aKzv.rst

@@ -0,0 +1,3 @@
+:c:func:`Py_REFCNT`, :c:func:`Py_TYPE`, :c:func:`Py_SIZE` and
+:c:func:`Py_IS_TYPE` functions argument type is now ``PyObject*``, rather
+than ``const PyObject*``. Patch by Victor Stinner.

Python/pystrhex.c

@@ -5,7 +5,7 @@
 #include <stdlib.h>               // abs()
 
 static PyObject *_Py_strhex_impl(const char* argbuf, const Py_ssize_t arglen,
-                                 const PyObject* sep, int bytes_per_sep_group,
+                                 PyObject* sep, int bytes_per_sep_group,
                                  const int return_bytes)
 {
     assert(arglen >= 0);
@@ -152,21 +152,23 @@ PyObject * _Py_strhex(const char* argbuf, const Py_ssize_t arglen)
 
 /* Same as above but returns a bytes() instead of str() to avoid the
  * need to decode the str() when bytes are needed. */
-PyObject * _Py_strhex_bytes(const char* argbuf, const Py_ssize_t arglen)
+PyObject* _Py_strhex_bytes(const char* argbuf, const Py_ssize_t arglen)
 {
     return _Py_strhex_impl(argbuf, arglen, NULL, 0, 1);
 }
 
 /* These variants include support for a separator between every N bytes: */
 
-PyObject * _Py_strhex_with_sep(const char* argbuf, const Py_ssize_t arglen, const PyObject* sep, const int bytes_per_group)
+PyObject* _Py_strhex_with_sep(const char* argbuf, const Py_ssize_t arglen,
+                              PyObject* sep, const int bytes_per_group)
 {
     return _Py_strhex_impl(argbuf, arglen, sep, bytes_per_group, 0);
 }
 
 /* Same as above but returns a bytes() instead of str() to avoid the
  * need to decode the str() when bytes are needed. */
-PyObject * _Py_strhex_bytes_with_sep(const char* argbuf, const Py_ssize_t arglen, const PyObject* sep, const int bytes_per_group)
+PyObject* _Py_strhex_bytes_with_sep(const char* argbuf, const Py_ssize_t arglen,
+                                    PyObject* sep, const int bytes_per_group)
 {
     return _Py_strhex_impl(argbuf, arglen, sep, bytes_per_group, 1);
 }