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, 4 insertions, 7 deletions

diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index cfc358f..3d8a216 100644
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -23,8 +23,6 @@ class bytes "PyBytesObject *" "&PyBytes_Type"
 
 #include "clinic/bytesobject.c.h"
 
-_Py_IDENTIFIER(__bytes__);
-
 /* PyBytesObject_SIZE gives the basic size of a bytes object; any memory allocation
    for a bytes object of length n should request PyBytesObject_SIZE + n bytes.
 
@@ -530,7 +528,7 @@ format_obj(PyObject *v, const char **pbuf, Py_ssize_t *plen)
         return v;
     }
     /* does it support __bytes__? */
-    func = _PyObject_LookupSpecial(v, &PyId___bytes__);
+    func = _PyObject_LookupSpecial(v, &_Py_ID(__bytes__));
     if (func != NULL) {
         result = _PyObject_CallNoArgs(func);
         Py_DECREF(func);
@@ -2582,7 +2580,7 @@ bytes_new_impl(PyTypeObject *type, PyObject *x, const char *encoding,
     /* We'd like to call PyObject_Bytes here, but we need to check for an
        integer argument before deferring to PyBytes_FromObject, something
        PyObject_Bytes doesn't do. */
-    else if ((func = _PyObject_LookupSpecial(x, &PyId___bytes__)) != NULL) {
+    else if ((func = _PyObject_LookupSpecial(x, &_Py_ID(__bytes__))) != NULL) {
         bytes = _PyObject_CallNoArgs(func);
         Py_DECREF(func);
         if (bytes == NULL)
@@ -3122,12 +3120,11 @@ PyDoc_STRVAR(length_hint_doc,
 static PyObject *
 striter_reduce(striterobject *it, PyObject *Py_UNUSED(ignored))
 {
-    _Py_IDENTIFIER(iter);
     if (it->it_seq != NULL) {
-        return Py_BuildValue("N(O)n", _PyEval_GetBuiltinId(&PyId_iter),
+        return Py_BuildValue("N(O)n", _PyEval_GetBuiltin(&_Py_ID(iter)),
                              it->it_seq, it->it_index);
     } else {
-        return Py_BuildValue("N(())", _PyEval_GetBuiltinId(&PyId_iter));
+        return Py_BuildValue("N(())", _PyEval_GetBuiltin(&_Py_ID(iter)));
     }
 }