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, 35 insertions, 1 deletions

diff --git a/Objects/call.c b/Objects/call.c
index 310a2d7..c3939ea 100644
--- a/Objects/call.c
+++ b/Objects/call.c
@@ -607,7 +607,6 @@ callmethod(PyThreadState *tstate, PyObject* callable, const char *format, va_lis
     return _PyObject_CallFunctionVa(tstate, callable, format, va, is_size_t);
 }
 
-
 PyObject *
 PyObject_CallMethod(PyObject *obj, const char *name, const char *format, ...)
 {
@@ -659,6 +658,30 @@ PyEval_CallMethod(PyObject *obj, const char *name, const char *format, ...)
 
 
 PyObject *
+_PyObject_CallMethod(PyObject *obj, PyObject *name,
+                     const char *format, ...)
+{
+    PyThreadState *tstate = _PyThreadState_GET();
+    if (obj == NULL || name == NULL) {
+        return null_error(tstate);
+    }
+
+    PyObject *callable = PyObject_GetAttr(obj, name);
+    if (callable == NULL) {
+        return NULL;
+    }
+
+    va_list va;
+    va_start(va, format);
+    PyObject *retval = callmethod(tstate, callable, format, va, 1);
+    va_end(va);
+
+    Py_DECREF(callable);
+    return retval;
+}
+
+
+PyObject *
 _PyObject_CallMethodId(PyObject *obj, _Py_Identifier *name,
                        const char *format, ...)
 {
@@ -682,6 +705,17 @@ _PyObject_CallMethodId(PyObject *obj, _Py_Identifier *name,
 }
 
 
+PyObject * _PyObject_CallMethodFormat(PyThreadState *tstate, PyObject *callable,
+                                      const char *format, ...)
+{
+    va_list va;
+    va_start(va, format);
+    PyObject *retval = callmethod(tstate, callable, format, va, 0);
+    va_end(va);
+    return retval;
+}
+
+
 PyObject *
 _PyObject_CallMethod_SizeT(PyObject *obj, const char *name,
                            const char *format, ...)