bpo-39573: Add Py_SET_TYPE() function (GH-18394)

Add Py_SET_TYPE() function to set the type of an object.

24 files changed, 77 insertions, 48 deletions

diff --git a/Doc/c-api/structures.rst b/Doc/c-api/structures.rst
index 100573c569..8a1431c2de 100644
--- a/Doc/c-api/structures.rst
+++ b/Doc/c-api/structures.rst
@@ -70,6 +70,13 @@ the definition of all other Python objects.
       (((PyObject*)(o))->ob_type)
 
 
+.. c:function:: void Py_SET_TYPE(PyObject *o, PyTypeObject *type)
+
+   Set the object *o* type to *type*.
+
+   .. versionadded:: 3.9
+
+
 .. c:macro:: Py_REFCNT(o)
 
    This macro is used to access the :attr:`ob_refcnt` member of a Python
diff --git a/Include/cpython/objimpl.h b/Include/cpython/objimpl.h
index 3f148146f6..ebb3e234e3 100644
--- a/Include/cpython/objimpl.h
+++ b/Include/cpython/objimpl.h
@@ -15,7 +15,7 @@ static inline PyObject*
 _PyObject_INIT(PyObject *op, PyTypeObject *typeobj)
 {
     assert(op != NULL);
-    Py_TYPE(op) = typeobj;
+    Py_SET_TYPE(op, typeobj);
     if (PyType_GetFlags(typeobj) & Py_TPFLAGS_HEAPTYPE) {
         Py_INCREF(typeobj);
     }
diff --git a/Include/object.h b/Include/object.h
index 0b63051337..eb887f4c6e 100644
--- a/Include/object.h
+++ b/Include/object.h
@@ -128,6 +128,12 @@ static inline void _Py_SET_REFCNT(PyObject *ob, Py_ssize_t refcnt) {
 }
 #define Py_SET_REFCNT(ob, refcnt) _Py_SET_REFCNT(_PyObject_CAST(ob), refcnt)
 
+static inline void _Py_SET_TYPE(PyObject *ob, PyTypeObject *type) {
+    ob->ob_type = type;
+}
+#define Py_SET_TYPE(ob, type) _Py_SET_TYPE(_PyObject_CAST(ob), type)
+
+
 /*
 Type objects contain a string containing the type name (to help somewhat
 in debugging), the allocation parameters (see PyObject_New() and
diff --git a/Misc/NEWS.d/next/C API/2020-02-07-03-39-03.bpo-39573.Oa8cL1.rst b/Misc/NEWS.d/next/C API/2020-02-07-03-39-03.bpo-39573.Oa8cL1.rst
new file mode 100644
index 0000000000..22d3d693ac
--- /dev/null
+++ b/Misc/NEWS.d/next/C API/2020-02-07-03-39-03.bpo-39573.Oa8cL1.rst
@@ -0,0 +1 @@
+Add :c:func:`Py_SET_TYPE` function to set the type of an object.
diff --git a/Modules/_blake2/blake2module.c b/Modules/_blake2/blake2module.c
index e2a3d420d4..9d280a9ccd 100644
--- a/Modules/_blake2/blake2module.c
+++ b/Modules/_blake2/blake2module.c
@@ -62,7 +62,7 @@ PyInit__blake2(void)
         return NULL;
 
     /* BLAKE2b */
-    Py_TYPE(&PyBlake2_BLAKE2bType) = &PyType_Type;
+    Py_SET_TYPE(&PyBlake2_BLAKE2bType, &PyType_Type);
     if (PyType_Ready(&PyBlake2_BLAKE2bType) < 0) {
         return NULL;
     }
@@ -82,7 +82,7 @@ PyInit__blake2(void)
     PyModule_AddIntConstant(m, "BLAKE2B_MAX_DIGEST_SIZE", BLAKE2B_OUTBYTES);
 
     /* BLAKE2s */
-    Py_TYPE(&PyBlake2_BLAKE2sType) = &PyType_Type;
+    Py_SET_TYPE(&PyBlake2_BLAKE2sType, &PyType_Type);
     if (PyType_Ready(&PyBlake2_BLAKE2sType) < 0) {
         return NULL;
     }
diff --git a/Modules/_ctypes/_ctypes.c b/Modules/_ctypes/_ctypes.c
index cb6e03f2ca..4747195c2e 100644
--- a/Modules/_ctypes/_ctypes.c
+++ b/Modules/_ctypes/_ctypes.c
@@ -5758,42 +5758,42 @@ PyInit__ctypes(void)
     if (PyType_Ready(&PyCData_Type) < 0)
         return NULL;
 
-    Py_TYPE(&Struct_Type) = &PyCStructType_Type;
+    Py_SET_TYPE(&Struct_Type, &PyCStructType_Type);
     Struct_Type.tp_base = &PyCData_Type;
     if (PyType_Ready(&Struct_Type) < 0)
         return NULL;
     Py_INCREF(&Struct_Type);
     PyModule_AddObject(m, "Structure", (PyObject *)&Struct_Type);
 
-    Py_TYPE(&Union_Type) = &UnionType_Type;
+    Py_SET_TYPE(&Union_Type, &UnionType_Type);
     Union_Type.tp_base = &PyCData_Type;
     if (PyType_Ready(&Union_Type) < 0)
         return NULL;
     Py_INCREF(&Union_Type);
     PyModule_AddObject(m, "Union", (PyObject *)&Union_Type);
 
-    Py_TYPE(&PyCPointer_Type) = &PyCPointerType_Type;
+    Py_SET_TYPE(&PyCPointer_Type, &PyCPointerType_Type);
     PyCPointer_Type.tp_base = &PyCData_Type;
     if (PyType_Ready(&PyCPointer_Type) < 0)
         return NULL;
     Py_INCREF(&PyCPointer_Type);
     PyModule_AddObject(m, "_Pointer", (PyObject *)&PyCPointer_Type);
 
-    Py_TYPE(&PyCArray_Type) = &PyCArrayType_Type;
+    Py_SET_TYPE(&PyCArray_Type, &PyCArrayType_Type);
     PyCArray_Type.tp_base = &PyCData_Type;
     if (PyType_Ready(&PyCArray_Type) < 0)
         return NULL;
     Py_INCREF(&PyCArray_Type);
     PyModule_AddObject(m, "Array", (PyObject *)&PyCArray_Type);
 
-    Py_TYPE(&Simple_Type) = &PyCSimpleType_Type;
+    Py_SET_TYPE(&Simple_Type, &PyCSimpleType_Type);
     Simple_Type.tp_base = &PyCData_Type;
     if (PyType_Ready(&Simple_Type) < 0)
         return NULL;
     Py_INCREF(&Simple_Type);
     PyModule_AddObject(m, "_SimpleCData", (PyObject *)&Simple_Type);
 
-    Py_TYPE(&PyCFuncPtr_Type) = &PyCFuncPtrType_Type;
+    Py_SET_TYPE(&PyCFuncPtr_Type, &PyCFuncPtrType_Type);
     PyCFuncPtr_Type.tp_base = &PyCData_Type;
     if (PyType_Ready(&PyCFuncPtr_Type) < 0)
         return NULL;
diff --git a/Modules/_ctypes/ctypes.h b/Modules/_ctypes/ctypes.h
index 351f996be0..a232a4bc83 100644
--- a/Modules/_ctypes/ctypes.h
+++ b/Modules/_ctypes/ctypes.h
@@ -68,7 +68,7 @@ typedef struct {
     ffi_type *atypes[1];
 } CThunkObject;
 extern PyTypeObject PyCThunk_Type;
-#define CThunk_CheckExact(v)        ((v)->ob_type == &PyCThunk_Type)
+#define CThunk_CheckExact(v)        (Py_TYPE(v) == &PyCThunk_Type)
 
 typedef struct {
     /* First part identical to tagCDataObject */
diff --git a/Modules/_sha3/sha3module.c b/Modules/_sha3/sha3module.c
index d4ca9a111d..9cdee5869a 100644
--- a/Modules/_sha3/sha3module.c
+++ b/Modules/_sha3/sha3module.c
@@ -713,7 +713,7 @@ PyInit__sha3(void)
 
 #define init_sha3type(name, type)     \
     do {                              \
-        Py_TYPE(type) = &PyType_Type; \
+        Py_SET_TYPE(type, &PyType_Type); \
         if (PyType_Ready(type) < 0) { \
             goto error;               \
         }                             \
diff --git a/Modules/_sqlite/prepare_protocol.c b/Modules/_sqlite/prepare_protocol.c
index 181c7edf96..05a2ca5a65 100644
--- a/Modules/_sqlite/prepare_protocol.c
+++ b/Modules/_sqlite/prepare_protocol.c
@@ -78,6 +78,6 @@ PyTypeObject pysqlite_PrepareProtocolType= {
 extern int pysqlite_prepare_protocol_setup_types(void)
 {
     pysqlite_PrepareProtocolType.tp_new = PyType_GenericNew;
-    Py_TYPE(&pysqlite_PrepareProtocolType)= &PyType_Type;
+    Py_SET_TYPE(&pysqlite_PrepareProtocolType, &PyType_Type);
     return PyType_Ready(&pysqlite_PrepareProtocolType);
 }
diff --git a/Modules/_testbuffer.c b/Modules/_testbuffer.c
index 047e3d3974..600a52aa87 100644
--- a/Modules/_testbuffer.c
+++ b/Modules/_testbuffer.c
@@ -2835,11 +2835,11 @@ PyInit__testbuffer(void)
     if (m == NULL)
         return NULL;
 
-    Py_TYPE(&NDArray_Type) = &PyType_Type;
+    Py_SET_TYPE(&NDArray_Type, &PyType_Type);
     Py_INCREF(&NDArray_Type);
     PyModule_AddObject(m, "ndarray", (PyObject *)&NDArray_Type);
 
-    Py_TYPE(&StaticArray_Type) = &PyType_Type;
+    Py_SET_TYPE(&StaticArray_Type, &PyType_Type);
     Py_INCREF(&StaticArray_Type);
     PyModule_AddObject(m, "staticarray", (PyObject *)&StaticArray_Type);
 
diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index 3bb1bf1e27..e6d30341cd 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -6605,9 +6605,9 @@ PyInit__testcapi(void)
     if (m == NULL)
         return NULL;
 
-    Py_TYPE(&_HashInheritanceTester_Type)=&PyType_Type;
+    Py_SET_TYPE(&_HashInheritanceTester_Type, &PyType_Type);
 
-    Py_TYPE(&test_structmembersType)=&PyType_Type;
+    Py_SET_TYPE(&test_structmembersType, &PyType_Type);
     Py_INCREF(&test_structmembersType);
     /* don't use a name starting with "test", since we don't want
        test_capi to automatically call this */
diff --git a/Modules/arraymodule.c b/Modules/arraymodule.c
index edb56ab6e1..5065d28daf 100644
--- a/Modules/arraymodule.c
+++ b/Modules/arraymodule.c
@@ -2996,7 +2996,7 @@ array_modexec(PyObject *m)
 
     if (PyType_Ready(&Arraytype) < 0)
         return -1;
-    Py_TYPE(&PyArrayIter_Type) = &PyType_Type;
+    Py_SET_TYPE(&PyArrayIter_Type, &PyType_Type);
 
     Py_INCREF((PyObject *)&Arraytype);
     if (PyModule_AddObject(m, "ArrayType", (PyObject *)&Arraytype) < 0) {
diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
index 0cb472966d..0dafb65c28 100644
--- a/Modules/itertoolsmodule.c
+++ b/Modules/itertoolsmodule.c
@@ -4750,14 +4750,16 @@ PyInit_itertools(void)
         NULL
     };
 
-    Py_TYPE(&teedataobject_type) = &PyType_Type;
+    Py_SET_TYPE(&teedataobject_type, &PyType_Type);
     m = PyModule_Create(&itertoolsmodule);
-    if (m == NULL)
+    if (m == NULL) {
         return NULL;
+    }
 
     for (i=0 ; typelist[i] != NULL ; i++) {
-        if (PyType_Ready(typelist[i]) < 0)
+        if (PyType_Ready(typelist[i]) < 0) {
             return NULL;
+        }
         name = _PyType_Name(typelist[i]);
         Py_INCREF(typelist[i]);
         PyModule_AddObject(m, name, (PyObject *)typelist[i]);
diff --git a/Modules/md5module.c b/Modules/md5module.c
index f2c2d32cbe..d783ae5a76 100644
--- a/Modules/md5module.c
+++ b/Modules/md5module.c
@@ -572,13 +572,15 @@ PyInit__md5(void)
 {
     PyObject *m;
 
-    Py_TYPE(&MD5type) = &PyType_Type;
-    if (PyType_Ready(&MD5type) < 0)
+    Py_SET_TYPE(&MD5type, &PyType_Type);
+    if (PyType_Ready(&MD5type) < 0) {
         return NULL;
+    }
 
     m = PyModule_Create(&_md5module);
-    if (m == NULL)
+    if (m == NULL) {
         return NULL;
+    }
 
     Py_INCREF((PyObject *)&MD5type);
     PyModule_AddObject(m, "MD5Type", (PyObject *)&MD5type);
diff --git a/Modules/sha1module.c b/Modules/sha1module.c
index 4d191c3c48..e066b88022 100644
--- a/Modules/sha1module.c
+++ b/Modules/sha1module.c
@@ -549,13 +549,15 @@ PyInit__sha1(void)
 {
     PyObject *m;
 
-    Py_TYPE(&SHA1type) = &PyType_Type;
-    if (PyType_Ready(&SHA1type) < 0)
+    Py_SET_TYPE(&SHA1type, &PyType_Type);
+    if (PyType_Ready(&SHA1type) < 0) {
         return NULL;
+    }
 
     m = PyModule_Create(&_sha1module);
-    if (m == NULL)
+    if (m == NULL) {
         return NULL;
+    }
 
     Py_INCREF((PyObject *)&SHA1type);
     PyModule_AddObject(m, "SHA1Type", (PyObject *)&SHA1type);
diff --git a/Modules/sha256module.c b/Modules/sha256module.c
index 245f4c0454..0e0c446188 100644
--- a/Modules/sha256module.c
+++ b/Modules/sha256module.c
@@ -713,12 +713,14 @@ PyInit__sha256(void)
 {
     PyObject *m;
 
-    Py_TYPE(&SHA224type) = &PyType_Type;
-    if (PyType_Ready(&SHA224type) < 0)
+    Py_SET_TYPE(&SHA224type, &PyType_Type);
+    if (PyType_Ready(&SHA224type) < 0) {
         return NULL;
-    Py_TYPE(&SHA256type) = &PyType_Type;
-    if (PyType_Ready(&SHA256type) < 0)
+    }
+    Py_SET_TYPE(&SHA256type, &PyType_Type);
+    if (PyType_Ready(&SHA256type) < 0) {
         return NULL;
+    }
 
     m = PyModule_Create(&_sha256module);
     if (m == NULL)
diff --git a/Modules/sha512module.c b/Modules/sha512module.c
index 4045698387..07bf283518 100644
--- a/Modules/sha512module.c
+++ b/Modules/sha512module.c
@@ -778,16 +778,19 @@ PyInit__sha512(void)
 {
     PyObject *m;
 
-    Py_TYPE(&SHA384type) = &PyType_Type;
-    if (PyType_Ready(&SHA384type) < 0)
+    Py_SET_TYPE(&SHA384type, &PyType_Type);
+    if (PyType_Ready(&SHA384type) < 0) {
         return NULL;
-    Py_TYPE(&SHA512type) = &PyType_Type;
-    if (PyType_Ready(&SHA512type) < 0)
+    }
+    Py_SET_TYPE(&SHA512type, &PyType_Type);
+    if (PyType_Ready(&SHA512type) < 0) {
         return NULL;
+    }
 
     m = PyModule_Create(&_sha512module);
-    if (m == NULL)
+    if (m == NULL) {
         return NULL;
+    }
 
     Py_INCREF((PyObject *)&SHA384type);
     PyModule_AddObject(m, "SHA384Type", (PyObject *)&SHA384type);
diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
index e54f7a9b1c..37b312396f 100644
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -7100,7 +7100,7 @@ PyInit__socket(void)
     }
 #endif
 
-    Py_TYPE(&sock_type) = &PyType_Type;
+    Py_SET_TYPE(&sock_type, &PyType_Type);
     m = PyModule_Create(&socketmodule);
     if (m == NULL)
         return NULL;
diff --git a/Modules/unicodedata.c b/Modules/unicodedata.c
index e99d914b79..58b1bc2d0a 100644
--- a/Modules/unicodedata.c
+++ b/Modules/unicodedata.c
@@ -1455,7 +1455,7 @@ PyInit_unicodedata(void)
 {
     PyObject *m, *v;
 
-    Py_TYPE(&UCD_Type) = &PyType_Type;
+    Py_SET_TYPE(&UCD_Type, &PyType_Type);
 
     m = PyModule_Create(&unicodedatamodule);
     if (!m)
diff --git a/Objects/floatobject.c b/Objects/floatobject.c
index 26e238cf05..dfc5b196f1 100644
--- a/Objects/floatobject.c
+++ b/Objects/floatobject.c
@@ -221,7 +221,7 @@ float_dealloc(PyFloatObject *op)
             return;
         }
         numfree++;
-        Py_TYPE(op) = (struct _typeobject *)free_list;
+        Py_SET_TYPE(op, (PyTypeObject *)free_list);
         free_list = op;
     }
     else
diff --git a/Objects/moduleobject.c b/Objects/moduleobject.c
index da329b4fba..0a593261c4 100644
--- a/Objects/moduleobject.c
+++ b/Objects/moduleobject.c
@@ -52,7 +52,7 @@ PyModuleDef_Init(struct PyModuleDef* def)
     if (def->m_base.m_index == 0) {
         max_module_number++;
         Py_SET_REFCNT(def, 1);
-        Py_TYPE(def) = &PyModuleDef_Type;
+        Py_SET_TYPE(def, &PyModuleDef_Type);
         def->m_base.m_index = max_module_number;
     }
     return (PyObject*)def;
diff --git a/Objects/object.c b/Objects/object.c
index 5806542488..503fb86780 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -144,7 +144,7 @@ PyObject_Init(PyObject *op, PyTypeObject *tp)
         return PyErr_NoMemory();
     }
 
-    Py_TYPE(op) = tp;
+    Py_SET_TYPE(op, tp);
     if (PyType_GetFlags(tp) & Py_TPFLAGS_HEAPTYPE) {
         Py_INCREF(tp);
     }
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 5b8d5a228e..e6a84b017a 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -4097,9 +4097,10 @@ object_set_class(PyObject *self, PyObject *value, void *closure)
     }
 
     if (compatible_for_assignment(oldto, newto, "__class__")) {
-        if (newto->tp_flags & Py_TPFLAGS_HEAPTYPE)
+        if (newto->tp_flags & Py_TPFLAGS_HEAPTYPE) {
             Py_INCREF(newto);
-        Py_TYPE(self) = newto;
+        }
+        Py_SET_TYPE(self, newto);
         if (oldto->tp_flags & Py_TPFLAGS_HEAPTYPE)
             Py_DECREF(oldto);
         return 0;
@@ -5334,8 +5335,9 @@ PyType_Ready(PyTypeObject *type)
        NULL when type is &PyBaseObject_Type, and we know its ob_type is
        not NULL (it's initialized to &PyType_Type).      But coverity doesn't
        know that. */
-    if (Py_TYPE(type) == NULL && base != NULL)
-        Py_TYPE(type) = Py_TYPE(base);
+    if (Py_TYPE(type) == NULL && base != NULL) {
+        Py_SET_TYPE(type, Py_TYPE(base));
+    }
 
     /* Initialize tp_bases */
     bases = type->tp_bases;
diff --git a/Objects/weakrefobject.c b/Objects/weakrefobject.c
index d104b646f0..18c737e7e4 100644
--- a/Objects/weakrefobject.c
+++ b/Objects/weakrefobject.c
@@ -882,10 +882,12 @@ PyWeakref_NewProxy(PyObject *ob, PyObject *callback)
         if (result != NULL) {
             PyWeakReference *prev;
 
-            if (PyCallable_Check(ob))
-                Py_TYPE(result) = &_PyWeakref_CallableProxyType;
-            else
-                Py_TYPE(result) = &_PyWeakref_ProxyType;
+            if (PyCallable_Check(ob)) {
+                Py_SET_TYPE(result, &_PyWeakref_CallableProxyType);
+            }
+            else {
+                Py_SET_TYPE(result, &_PyWeakref_ProxyType);
+            }
             get_basic_refs(*list, &ref, &proxy);
             if (callback == NULL) {
                 if (proxy != NULL) {