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, 3 deletions

diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index 0c7d4de0686..721c9a63d51 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -55,6 +55,7 @@ raised for division by zero and mod by zero.
 #ifndef Py_BUILD_CORE_BUILTIN
 #  define Py_BUILD_CORE_MODULE 1
 #endif
+#define NEEDS_PY_IDENTIFIER
 
 #include "Python.h"
 #include "pycore_bitutils.h"      // _Py_bit_length()
@@ -1216,7 +1217,7 @@ math_ceil(PyObject *module, PyObject *number)
     _Py_IDENTIFIER(__ceil__);
 
     if (!PyFloat_CheckExact(number)) {
-        PyObject *method = _PyObject_LookupSpecial(number, &PyId___ceil__);
+        PyObject *method = _PyObject_LookupSpecialId(number, &PyId___ceil__);
         if (method != NULL) {
             PyObject *result = _PyObject_CallNoArgs(method);
             Py_DECREF(method);
@@ -1288,7 +1289,7 @@ math_floor(PyObject *module, PyObject *number)
     }
     else
     {
-        PyObject *method = _PyObject_LookupSpecial(number, &PyId___floor__);
+        PyObject *method = _PyObject_LookupSpecialId(number, &PyId___floor__);
         if (method != NULL) {
             PyObject *result = _PyObject_CallNoArgs(method);
             Py_DECREF(method);
@@ -2166,7 +2167,7 @@ math_trunc(PyObject *module, PyObject *x)
             return NULL;
     }
 
-    trunc = _PyObject_LookupSpecial(x, &PyId___trunc__);
+    trunc = _PyObject_LookupSpecialId(x, &PyId___trunc__);
     if (trunc == NULL) {
         if (!PyErr_Occurred())
             PyErr_Format(PyExc_TypeError,