bpo-46541: Replace core use of _Py_IDENTIFIER() with statically initialized global objects. (gh-30928)

We're no longer using _Py_IDENTIFIER() (or _Py_static_string()) in any core CPython code.  It is still used in a number of non-builtin stdlib modules.

The replacement is: PyUnicodeObject (not pointer) fields under _PyRuntimeState, statically initialized as part of _PyRuntime.  A new _Py_GET_GLOBAL_IDENTIFIER() macro facilitates lookup of the fields (along with _Py_GET_GLOBAL_STRING() for non-identifier strings).

https://bugs.python.org/issue46541#msg411799 explains the rationale for this change.

The core of the change is in:

* (new) Include/internal/pycore_global_strings.h - the declarations for the global strings, along with the macros
* Include/internal/pycore_runtime_init.h - added the static initializers for the global strings
* Include/internal/pycore_global_objects.h - where the struct in pycore_global_strings.h is hooked into _PyRuntimeState
* Tools/scripts/generate_global_objects.py - added generation of the global string declarations and static initializers

I've also added a --check flag to generate_global_objects.py (along with make check-global-objects) to check for unused global strings.  That check is added to the PR CI config.

The remainder of this change updates the core code to use _Py_GET_GLOBAL_IDENTIFIER() instead of _Py_IDENTIFIER() and the related _Py*Id functions (likewise for _Py_GET_GLOBAL_STRING() instead of _Py_static_string()).  This includes adding a few functions where there wasn't already an alternative to _Py*Id(), replacing the _Py_Identifier * parameter with PyObject *.

The following are not changed (yet):

* stop using _Py_IDENTIFIER() in the stdlib modules
* (maybe) get rid of _Py_IDENTIFIER(), etc. entirely -- this may not be doable as at least one package on PyPI using this (private) API
* (maybe) intern the strings during runtime init

https://bugs.python.org/issue46541

1 files changed, 21 insertions, 28 deletions

diff --git a/Modules/_abc.c b/Modules/_abc.c
index a0439618120..641d6198d1f 100644
--- a/Modules/_abc.c
+++ b/Modules/_abc.c
@@ -4,8 +4,9 @@
 #endif
 
 #include "Python.h"
-#include "pycore_object.h"        // _PyType_GetSubclasses()
 #include "pycore_moduleobject.h"  // _PyModule_GetState()
+#include "pycore_object.h"        // _PyType_GetSubclasses()
+#include "pycore_runtime.h"       // _Py_ID()
 #include "clinic/_abc.c.h"
 
 /*[clinic input]
@@ -16,15 +17,6 @@ module _abc
 PyDoc_STRVAR(_abc__doc__,
 "Module contains faster C implementation of abc.ABCMeta");
 
-_Py_IDENTIFIER(__abstractmethods__);
-_Py_IDENTIFIER(__class__);
-_Py_IDENTIFIER(__dict__);
-_Py_IDENTIFIER(__abc_tpflags__);
-_Py_IDENTIFIER(__bases__);
-_Py_IDENTIFIER(_abc_impl);
-_Py_IDENTIFIER(__subclasscheck__);
-_Py_IDENTIFIER(__subclasshook__);
-
 typedef struct {
     PyTypeObject *_abc_data_type;
     unsigned long long abc_invalidation_counter;
@@ -122,7 +114,7 @@ static _abc_data *
 _get_impl(PyObject *module, PyObject *self)
 {
     _abcmodule_state *state = get_abc_state(module);
-    PyObject *impl = _PyObject_GetAttrId(self, &PyId__abc_impl);
+    PyObject *impl = PyObject_GetAttr(self, &_Py_ID(_abc_impl));
     if (impl == NULL) {
         return NULL;
     }
@@ -311,7 +303,7 @@ compute_abstract_methods(PyObject *self)
     PyObject *ns = NULL, *items = NULL, *bases = NULL;  // Py_XDECREF()ed on error.
 
     /* Stage 1: direct abstract methods. */
-    ns = _PyObject_GetAttrId(self, &PyId___dict__);
+    ns = PyObject_GetAttr(self, &_Py_ID(__dict__));
     if (!ns) {
         goto error;
     }
@@ -355,7 +347,7 @@ compute_abstract_methods(PyObject *self)
     }
 
     /* Stage 2: inherited abstract methods. */
-    bases = _PyObject_GetAttrId(self, &PyId___bases__);
+    bases = PyObject_GetAttr(self, &_Py_ID(__bases__));
     if (!bases) {
         goto error;
     }
@@ -368,8 +360,8 @@ compute_abstract_methods(PyObject *self)
         PyObject *item = PyTuple_GET_ITEM(bases, pos);  // borrowed
         PyObject *base_abstracts, *iter;
 
-        if (_PyObject_LookupAttrId(item, &PyId___abstractmethods__,
-                                   &base_abstracts) < 0) {
+        if (_PyObject_LookupAttr(item, &_Py_ID(__abstractmethods__),
+                                 &base_abstracts) < 0) {
             goto error;
         }
         if (base_abstracts == NULL) {
@@ -409,7 +401,7 @@ compute_abstract_methods(PyObject *self)
         }
     }
 
-    if (_PyObject_SetAttrId(self, &PyId___abstractmethods__, abstracts) < 0) {
+    if (PyObject_SetAttr(self, &_Py_ID(__abstractmethods__), abstracts) < 0) {
         goto error;
     }
 
@@ -448,7 +440,7 @@ _abc__abc_init(PyObject *module, PyObject *self)
     if (data == NULL) {
         return NULL;
     }
-    if (_PyObject_SetAttrId(self, &PyId__abc_impl, data) < 0) {
+    if (PyObject_SetAttr(self, &_Py_ID(_abc_impl), data) < 0) {
         Py_DECREF(data);
         return NULL;
     }
@@ -459,7 +451,8 @@ _abc__abc_init(PyObject *module, PyObject *self)
      * their special status w.r.t. pattern matching. */
     if (PyType_Check(self)) {
         PyTypeObject *cls = (PyTypeObject *)self;
-        PyObject *flags = _PyDict_GetItemIdWithError(cls->tp_dict, &PyId___abc_tpflags__);
+        PyObject *flags = PyDict_GetItemWithError(cls->tp_dict,
+                                                  &_Py_ID(__abc_tpflags__));
         if (flags == NULL) {
             if (PyErr_Occurred()) {
                 return NULL;
@@ -477,7 +470,7 @@ _abc__abc_init(PyObject *module, PyObject *self)
                 }
                 ((PyTypeObject *)self)->tp_flags |= (val & COLLECTION_FLAGS);
             }
-            if (_PyDict_DelItemId(cls->tp_dict, &PyId___abc_tpflags__) < 0) {
+            if (PyDict_DelItem(cls->tp_dict, &_Py_ID(__abc_tpflags__)) < 0) {
                 return NULL;
             }
         }
@@ -593,7 +586,7 @@ _abc__abc_instancecheck_impl(PyObject *module, PyObject *self,
         return NULL;
     }
 
-    subclass = _PyObject_GetAttrId(instance, &PyId___class__);
+    subclass = PyObject_GetAttr(instance, &_Py_ID(__class__));
     if (subclass == NULL) {
         Py_DECREF(impl);
         return NULL;
@@ -622,12 +615,12 @@ _abc__abc_instancecheck_impl(PyObject *module, PyObject *self,
             }
         }
         /* Fall back to the subclass check. */
-        result = _PyObject_CallMethodIdOneArg(self, &PyId___subclasscheck__,
-                                              subclass);
+        result = PyObject_CallMethodOneArg(self, &_Py_ID(__subclasscheck__),
+                                           subclass);
         goto end;
     }
-    result = _PyObject_CallMethodIdOneArg(self, &PyId___subclasscheck__,
-                                          subclass);
+    result = PyObject_CallMethodOneArg(self, &_Py_ID(__subclasscheck__),
+                                       subclass);
     if (result == NULL) {
         goto end;
     }
@@ -639,8 +632,8 @@ _abc__abc_instancecheck_impl(PyObject *module, PyObject *self,
         break;
     case 0:
         Py_DECREF(result);
-        result = _PyObject_CallMethodIdOneArg(self, &PyId___subclasscheck__,
-                                              subtype);
+        result = PyObject_CallMethodOneArg(self, &_Py_ID(__subclasscheck__),
+                                           subtype);
         break;
     case 1:  // Nothing to do.
         break;
@@ -723,8 +716,8 @@ _abc__abc_subclasscheck_impl(PyObject *module, PyObject *self,
     }
 
     /* 3. Check the subclass hook. */
-    ok = _PyObject_CallMethodIdOneArg((PyObject *)self, &PyId___subclasshook__,
-                                      subclass);
+    ok = PyObject_CallMethodOneArg(
+            (PyObject *)self, &_Py_ID(__subclasshook__), subclass);
     if (ok == NULL) {
         goto end;
     }