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, 2 deletions

diff --git a/Python/importdl.c b/Python/importdl.c
index 6d25547..f66c601 100644
--- a/Python/importdl.c
+++ b/Python/importdl.c
@@ -2,6 +2,9 @@
 /* Support for dynamic loading of extension modules */
 
 #include "Python.h"
+#include "pycore_call.h"
+#include "pycore_pystate.h"
+#include "pycore_runtime.h"
 
 /* ./configure sets HAVE_DYNAMIC_LOADING if dynamic loading of modules is
    supported on this platform. configure will then compile and link in one
@@ -38,7 +41,6 @@ get_encoded_name(PyObject *name, const char **hook_prefix) {
     PyObject *encoded = NULL;
     PyObject *modname = NULL;
     Py_ssize_t name_len, lastdot;
-    _Py_IDENTIFIER(replace);
 
     /* Get the short name (substring after last dot) */
     name_len = PyUnicode_GetLength(name);
@@ -76,7 +78,7 @@ get_encoded_name(PyObject *name, const char **hook_prefix) {
     }
 
     /* Replace '-' by '_' */
-    modname = _PyObject_CallMethodId(encoded, &PyId_replace, "cc", '-', '_');
+    modname = _PyObject_CallMethod(encoded, &_Py_ID(replace), "cc", '-', '_');
     if (modname == NULL)
         goto error;