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, 8 insertions, 14 deletions

diff --git a/Objects/fileobject.c b/Objects/fileobject.c
index 8ca56a8..8dba5b9 100644
--- a/Objects/fileobject.c
+++ b/Objects/fileobject.c
@@ -26,8 +26,6 @@
 extern "C" {
 #endif
 
-_Py_IDENTIFIER(open);
-
 /* External C interface */
 
 PyObject *
@@ -40,9 +38,9 @@ PyFile_FromFd(int fd, const char *name, const char *mode, int buffering, const c
     io = PyImport_ImportModule("_io");
     if (io == NULL)
         return NULL;
-    stream = _PyObject_CallMethodId(io, &PyId_open, "isisssO", fd, mode,
-                                 buffering, encoding, errors,
-                                 newline, closefd ? Py_True : Py_False);
+    stream = _PyObject_CallMethod(io, &_Py_ID(open), "isisssO", fd, mode,
+                                  buffering, encoding, errors,
+                                  newline, closefd ? Py_True : Py_False);
     Py_DECREF(io);
     if (stream == NULL)
         return NULL;
@@ -54,7 +52,6 @@ PyFile_FromFd(int fd, const char *name, const char *mode, int buffering, const c
 PyObject *
 PyFile_GetLine(PyObject *f, int n)
 {
-    _Py_IDENTIFIER(readline);
     PyObject *result;
 
     if (f == NULL) {
@@ -63,10 +60,10 @@ PyFile_GetLine(PyObject *f, int n)
     }
 
     if (n <= 0) {
-        result = _PyObject_CallMethodIdNoArgs(f, &PyId_readline);
+        result = PyObject_CallMethodNoArgs(f, &_Py_ID(readline));
     }
     else {
-        result = _PyObject_CallMethodId(f, &PyId_readline, "i", n);
+        result = _PyObject_CallMethod(f, &_Py_ID(readline), "i", n);
     }
     if (result != NULL && !PyBytes_Check(result) &&
         !PyUnicode_Check(result)) {
@@ -120,13 +117,12 @@ int
 PyFile_WriteObject(PyObject *v, PyObject *f, int flags)
 {
     PyObject *writer, *value, *result;
-    _Py_IDENTIFIER(write);
 
     if (f == NULL) {
         PyErr_SetString(PyExc_TypeError, "writeobject with NULL file");
         return -1;
     }
-    writer = _PyObject_GetAttrId(f, &PyId_write);
+    writer = PyObject_GetAttr(f, &_Py_ID(write));
     if (writer == NULL)
         return -1;
     if (flags & Py_PRINT_RAW) {
@@ -182,12 +178,11 @@ PyObject_AsFileDescriptor(PyObject *o)
 {
     int fd;
     PyObject *meth;
-    _Py_IDENTIFIER(fileno);
 
     if (PyLong_Check(o)) {
         fd = _PyLong_AsInt(o);
     }
-    else if (_PyObject_LookupAttrId(o, &PyId_fileno, &meth) < 0) {
+    else if (_PyObject_LookupAttr(o, &_Py_ID(fileno), &meth) < 0) {
         return -1;
     }
     else if (meth != NULL) {
@@ -509,8 +504,7 @@ PyFile_OpenCodeObject(PyObject *path)
     } else {
         iomod = PyImport_ImportModule("_io");
         if (iomod) {
-            f = _PyObject_CallMethodId(iomod, &PyId_open, "Os",
-                                       path, "rb");
+            f = _PyObject_CallMethod(iomod, &_Py_ID(open), "Os", path, "rb");
             Py_DECREF(iomod);
         }
     }