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, 10 insertions, 9 deletions

diff --git a/Parser/tokenizer.c b/Parser/tokenizer.c
index d38df66..b14506a 100644
--- a/Parser/tokenizer.c
+++ b/Parser/tokenizer.c
@@ -443,8 +443,6 @@ static int
 fp_setreadl(struct tok_state *tok, const char* enc)
 {
     PyObject *readline, *io, *stream;
-    _Py_IDENTIFIER(open);
-    _Py_IDENTIFIER(readline);
     int fd;
     long pos;
 
@@ -462,25 +460,28 @@ fp_setreadl(struct tok_state *tok, const char* enc)
     }
 
     io = PyImport_ImportModule("io");
-    if (io == NULL)
+    if (io == NULL) {
         return 0;
-
-    stream = _PyObject_CallMethodId(io, &PyId_open, "isisOOO",
+    }
+    stream = _PyObject_CallMethod(io, &_Py_ID(open), "isisOOO",
                     fd, "r", -1, enc, Py_None, Py_None, Py_False);
     Py_DECREF(io);
-    if (stream == NULL)
+    if (stream == NULL) {
         return 0;
+    }
 
-    readline = _PyObject_GetAttrId(stream, &PyId_readline);
+    readline = PyObject_GetAttr(stream, &_Py_ID(readline));
     Py_DECREF(stream);
-    if (readline == NULL)
+    if (readline == NULL) {
         return 0;
+    }
     Py_XSETREF(tok->decoding_readline, readline);
 
     if (pos > 0) {
         PyObject *bufobj = _PyObject_CallNoArgs(readline);
-        if (bufobj == NULL)
+        if (bufobj == NULL) {
             return 0;
+        }
         Py_DECREF(bufobj);
     }