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

4 files changed, 8 insertions, 0 deletions

diff --git a/Modules/_sqlite/connection.c b/Modules/_sqlite/connection.c
index caefdf4..cb8cd2a 100644
--- a/Modules/_sqlite/connection.c
+++ b/Modules/_sqlite/connection.c
@@ -21,6 +21,8 @@
  * 3. This notice may not be removed or altered from any source distribution.
  */
 
+#define NEEDS_PY_IDENTIFIER
+
 #include "module.h"
 #include "structmember.h"         // PyMemberDef
 #include "connection.h"
diff --git a/Modules/_sqlite/cursor.c b/Modules/_sqlite/cursor.c
index 4700afb..395b10f 100644
--- a/Modules/_sqlite/cursor.c
+++ b/Modules/_sqlite/cursor.c
@@ -21,6 +21,8 @@
  * 3. This notice may not be removed or altered from any source distribution.
  */
 
+#define NEEDS_PY_IDENTIFIER
+
 #include "cursor.h"
 #include "module.h"
 #include "util.h"
diff --git a/Modules/_sqlite/microprotocols.c b/Modules/_sqlite/microprotocols.c
index 95c799d..697d1a7 100644
--- a/Modules/_sqlite/microprotocols.c
+++ b/Modules/_sqlite/microprotocols.c
@@ -23,6 +23,8 @@
  * 3. This notice may not be removed or altered from any source distribution.
  */
 
+#define NEEDS_PY_IDENTIFIER
+
 #include <Python.h>
 
 #include "cursor.h"
diff --git a/Modules/_sqlite/module.c b/Modules/_sqlite/module.c
index 3b9f797..cfa4b97 100644
--- a/Modules/_sqlite/module.c
+++ b/Modules/_sqlite/module.c
@@ -21,6 +21,8 @@
  * 3. This notice may not be removed or altered from any source distribution.
  */
 
+#define NEEDS_PY_IDENTIFIER
+
 #include "connection.h"
 #include "statement.h"
 #include "cursor.h"