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, 8 deletions

diff --git a/Objects/funcobject.c b/Objects/funcobject.c
index a8f006da8ad..deacfd55dd2 100644
--- a/Objects/funcobject.c
+++ b/Objects/funcobject.c
@@ -79,8 +79,7 @@ PyFunction_NewWithQualName(PyObject *code, PyObject *globals, PyObject *qualname
     Py_INCREF(doc);
 
     // __module__: Use globals['__name__'] if it exists, or NULL.
-    _Py_IDENTIFIER(__name__);
-    PyObject *module = _PyDict_GetItemIdWithError(globals, &PyId___name__);
+    PyObject *module = PyDict_GetItemWithError(globals, &_Py_ID(__name__));
     PyObject *builtins = NULL;
     if (module == NULL && _PyErr_Occurred(tstate)) {
         goto error;
@@ -808,12 +807,7 @@ functools_wraps(PyObject *wrapper, PyObject *wrapped)
 {
 #define COPY_ATTR(ATTR) \
     do { \
-        _Py_IDENTIFIER(ATTR); \
-        PyObject *attr = _PyUnicode_FromId(&PyId_ ## ATTR); \
-        if (attr == NULL) { \
-            return -1; \
-        } \
-        if (functools_copy_attr(wrapper, wrapped, attr) < 0) { \
+        if (functools_copy_attr(wrapper, wrapped, &_Py_ID(ATTR)) < 0) { \
             return -1; \
         } \
     } while (0) \