gh-118527: Intern code consts in free-threaded build (#118667)

We already intern and immortalize most string constants. In the
free-threaded build, other constants can be a source of reference count
contention because they are shared by all threads running the same code
objects.

Python/bltinmodule.c

@@ -866,8 +866,21 @@ builtin_compile_impl(PyObject *module, PyObject *source, PyObject *filename,
     if (str == NULL)
         goto error;
 
+#ifdef Py_GIL_DISABLED
+    // gh-118527: Disable immortalization of code constants for explicit
+    // compile() calls to get consistent frozen outputs between the default
+    // and free-threaded builds.
+    PyInterpreterState *interp = _PyInterpreterState_GET();
+    int old_value = interp->gc.immortalize.enable_on_thread_created;
+    interp->gc.immortalize.enable_on_thread_created = 0;
+#endif
+
     result = Py_CompileStringObject(str, filename, start[compile_mode], &cf, optimize);
 
+#ifdef Py_GIL_DISABLED
+    interp->gc.immortalize.enable_on_thread_created = old_value;
+#endif
+
     Py_XDECREF(source_copy);
     goto finally;
 

Python/pylifecycle.c

@@ -854,6 +854,11 @@ pycore_interp_init(PyThreadState *tstate)
         return status;
     }
 
+    status = _PyCode_Init(interp);
+    if (_PyStatus_EXCEPTION(status)) {
+        return status;
+    }
+
     status = _PyDtoa_Init(interp);
     if (_PyStatus_EXCEPTION(status)) {
         return status;
@@ -1827,6 +1832,8 @@ finalize_interp_types(PyInterpreterState *interp)
 
     _PyTypes_Fini(interp);
 
+    _PyCode_Fini(interp);
+
     // Call _PyUnicode_ClearInterned() before _PyDict_Fini() since it uses
     // a dict internally.
     _PyUnicode_ClearInterned(interp);

Python/pystate.c

@@ -404,6 +404,7 @@ _Py_COMP_DIAG_POP
         &(runtime)->audit_hooks.mutex, \
         &(runtime)->allocators.mutex, \
         &(runtime)->_main_interpreter.types.mutex, \
+        &(runtime)->_main_interpreter.code_state.mutex, \
     }
 
 static void