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, 2 insertions, 4 deletions

diff --git a/Objects/genobject.c b/Objects/genobject.c
index b2d402e..b34931a 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -320,7 +320,6 @@ static int
 gen_close_iter(PyObject *yf)
 {
     PyObject *retval = NULL;
-    _Py_IDENTIFIER(close);
 
     if (PyGen_CheckExact(yf) || PyCoro_CheckExact(yf)) {
         retval = gen_close((PyGenObject *)yf, NULL);
@@ -329,7 +328,7 @@ gen_close_iter(PyObject *yf)
     }
     else {
         PyObject *meth;
-        if (_PyObject_LookupAttrId(yf, &PyId_close, &meth) < 0) {
+        if (_PyObject_LookupAttr(yf, &_Py_ID(close), &meth) < 0) {
             PyErr_WriteUnraisable(yf);
         }
         if (meth) {
@@ -417,7 +416,6 @@ _gen_throw(PyGenObject *gen, int close_on_genexit,
            PyObject *typ, PyObject *val, PyObject *tb)
 {
     PyObject *yf = _PyGen_yf(gen);
-    _Py_IDENTIFIER(throw);
 
     if (yf) {
         InterpreterFrame *frame = (InterpreterFrame *)gen->gi_iframe;
@@ -462,7 +460,7 @@ _gen_throw(PyGenObject *gen, int close_on_genexit,
         } else {
             /* `yf` is an iterator or a coroutine-like object. */
             PyObject *meth;
-            if (_PyObject_LookupAttrId(yf, &PyId_throw, &meth) < 0) {
+            if (_PyObject_LookupAttr(yf, &_Py_ID(throw), &meth) < 0) {
                 Py_DECREF(yf);
                 return NULL;
             }