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, 6 insertions, 10 deletions

diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
index 342a3e6..0ec65d5 100644
--- a/Modules/itertoolsmodule.c
+++ b/Modules/itertoolsmodule.c
@@ -503,9 +503,8 @@ _grouper_next(_grouperobject *igo)
 static PyObject *
 _grouper_reduce(_grouperobject *lz, PyObject *Py_UNUSED(ignored))
 {
-    _Py_IDENTIFIER(iter);
     if (((groupbyobject *)lz->parent)->currgrouper != lz) {
-        return Py_BuildValue("N(())", _PyEval_GetBuiltinId(&PyId_iter));
+        return Py_BuildValue("N(())", _PyEval_GetBuiltin(&_Py_ID(iter)));
     }
     return Py_BuildValue("O(OO)", Py_TYPE(lz), lz->parent, lz->tgtkey);
 }
@@ -1015,7 +1014,6 @@ itertools_tee_impl(PyObject *module, PyObject *iterable, Py_ssize_t n)
 {
     Py_ssize_t i;
     PyObject *it, *copyable, *copyfunc, *result;
-    _Py_IDENTIFIER(__copy__);
 
     if (n < 0) {
         PyErr_SetString(PyExc_ValueError, "n must be >= 0");
@@ -1032,7 +1030,7 @@ itertools_tee_impl(PyObject *module, PyObject *iterable, Py_ssize_t n)
         return NULL;
     }
 
-    if (_PyObject_LookupAttrId(it, &PyId___copy__, &copyfunc) < 0) {
+    if (_PyObject_LookupAttr(it, &_Py_ID(__copy__), &copyfunc) < 0) {
         Py_DECREF(it);
         Py_DECREF(result);
         return NULL;
@@ -1047,7 +1045,7 @@ itertools_tee_impl(PyObject *module, PyObject *iterable, Py_ssize_t n)
             Py_DECREF(result);
             return NULL;
         }
-        copyfunc = _PyObject_GetAttrId(copyable, &PyId___copy__);
+        copyfunc = PyObject_GetAttr(copyable, &_Py_ID(__copy__));
         if (copyfunc == NULL) {
             Py_DECREF(copyable);
             Py_DECREF(result);
@@ -1179,9 +1177,8 @@ cycle_reduce(cycleobject *lz, PyObject *Py_UNUSED(ignored))
         if (it == NULL)
             return NULL;
         if (lz->index != 0) {
-            _Py_IDENTIFIER(__setstate__);
-            PyObject *res = _PyObject_CallMethodId(it, &PyId___setstate__,
-                                                   "n", lz->index);
+            PyObject *res = _PyObject_CallMethod(it, &_Py_ID(__setstate__),
+                                                 "n", lz->index);
             if (res == NULL) {
                 Py_DECREF(it);
                 return NULL;
@@ -4545,7 +4542,6 @@ static PyTypeObject ziplongest_type;
 static PyObject *
 zip_longest_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 {
-    _Py_IDENTIFIER(fillvalue);
     ziplongestobject *lz;
     Py_ssize_t i;
     PyObject *ittuple;  /* tuple of iterators */
@@ -4556,7 +4552,7 @@ zip_longest_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
     if (kwds != NULL && PyDict_CheckExact(kwds) && PyDict_GET_SIZE(kwds) > 0) {
         fillvalue = NULL;
         if (PyDict_GET_SIZE(kwds) == 1) {
-            fillvalue = _PyDict_GetItemIdWithError(kwds, &PyId_fillvalue);
+            fillvalue = PyDict_GetItemWithError(kwds, &_Py_ID(fillvalue));
         }
         if (fillvalue == NULL) {
             if (!PyErr_Occurred()) {