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, 9 deletions

diff --git a/Objects/classobject.c b/Objects/classobject.c
index 9d4fc99..d7ccf31 100644
--- a/Objects/classobject.c
+++ b/Objects/classobject.c
@@ -9,8 +9,6 @@
 
 #define TP_DESCR_GET(t) ((t)->tp_descr_get)
 
-_Py_IDENTIFIER(__name__);
-_Py_IDENTIFIER(__qualname__);
 
 PyObject *
 PyMethod_Function(PyObject *im)
@@ -123,14 +121,13 @@ method_reduce(PyMethodObject *im, PyObject *Py_UNUSED(ignored))
     PyObject *self = PyMethod_GET_SELF(im);
     PyObject *func = PyMethod_GET_FUNCTION(im);
     PyObject *funcname;
-    _Py_IDENTIFIER(getattr);
 
-    funcname = _PyObject_GetAttrId(func, &PyId___name__);
+    funcname = PyObject_GetAttr(func, &_Py_ID(__name__));
     if (funcname == NULL) {
         return NULL;
     }
-    return Py_BuildValue("N(ON)", _PyEval_GetBuiltinId(&PyId_getattr),
-                         self, funcname);
+    return Py_BuildValue(
+            "N(ON)", _PyEval_GetBuiltin(&_Py_ID(getattr)), self, funcname);
 }
 
 static PyMethodDef method_methods[] = {
@@ -280,9 +277,9 @@ method_repr(PyMethodObject *a)
     PyObject *funcname, *result;
     const char *defname = "?";
 
-    if (_PyObject_LookupAttrId(func, &PyId___qualname__, &funcname) < 0 ||
+    if (_PyObject_LookupAttr(func, &_Py_ID(__qualname__), &funcname) < 0 ||
         (funcname == NULL &&
-         _PyObject_LookupAttrId(func, &PyId___name__, &funcname) < 0))
+         _PyObject_LookupAttr(func, &_Py_ID(__name__), &funcname) < 0))
     {
         return NULL;
     }
@@ -515,7 +512,7 @@ instancemethod_repr(PyObject *self)
         return NULL;
     }
 
-    if (_PyObject_LookupAttrId(func, &PyId___name__, &funcname) < 0) {
+    if (_PyObject_LookupAttr(func, &_Py_ID(__name__), &funcname) < 0) {
         return NULL;
     }
     if (funcname != NULL && !PyUnicode_Check(funcname)) {