GH-90699: disallow _Py_IDENTIFIER in core code (GH-99210)

Include/cpython/object.h

@@ -41,15 +41,15 @@ typedef struct _Py_Identifier {
     Py_ssize_t index;
 } _Py_Identifier;
 
-#if defined(NEEDS_PY_IDENTIFIER) || !defined(Py_BUILD_CORE)
+#ifndef Py_BUILD_CORE
 // For now we are keeping _Py_IDENTIFIER for continued use
 // in non-builtin extensions (and naughty PyPI modules).
 
 #define _Py_static_string_init(value) { .string = (value), .index = -1 }
 #define _Py_static_string(varname, value)  static _Py_Identifier varname = _Py_static_string_init(value)
 #define _Py_IDENTIFIER(varname) _Py_static_string(PyId_##varname, #varname)
 
-#endif  /* NEEDS_PY_IDENTIFIER */
+#endif /* !Py_BUILD_CORE */
 
 typedef struct {
     /* Number implementations must check *both*

Programs/_testembed.c

@@ -1,7 +1,6 @@
 #ifndef Py_BUILD_CORE_MODULE
 #  define Py_BUILD_CORE_MODULE
 #endif
-#define NEEDS_PY_IDENTIFIER
 
 /* Always enable assertion (even in release mode) */
 #undef NDEBUG
@@ -1891,7 +1890,14 @@ static int test_unicode_id_init(void)
 {
     // bpo-42882: Test that _PyUnicode_FromId() works
     // when Python is initialized multiples times.
-    _Py_IDENTIFIER(test_unicode_id_init);
+
+    // This is equivalent to `_Py_IDENTIFIER(test_unicode_id_init)`
+    // but since `_Py_IDENTIFIER` is disabled when `Py_BUILD_CORE`
+    // is defined, it is manually expanded here.
+    static _Py_Identifier PyId_test_unicode_id_init = {
+        .string = "test_unicode_id_init",
+        .index = -1,
+    };
 
     // Initialize Python once without using the identifier
     _testembed_Py_InitializeFromConfig();