1 files changed, 30 insertions, 0 deletions
diff --git a/variable.c b/variable.c
index f80f1a56a6..0a5ec60c25 100644
--- a/variable.c
+++ b/variable.c
@@ -1464,6 +1464,36 @@ rb_ivar_get(VALUE obj, ID id)
 }
 
 VALUE
+rb_ivar_get_at(VALUE obj, attr_index_t index, ID id)
+{
+    RUBY_ASSERT(rb_is_instance_id(id));
+    // Used by JITs, but never for T_OBJECT.
+
+    switch (BUILTIN_TYPE(obj)) {
+      case T_OBJECT:
+        UNREACHABLE_RETURN(Qundef);
+      case T_CLASS:
+      case T_MODULE:
+        {
+            VALUE fields_obj = RCLASS_WRITABLE_FIELDS_OBJ(obj);
+            VALUE val = rb_imemo_fields_ptr(fields_obj)[index];
+
+            if (UNLIKELY(!rb_ractor_main_p()) && !rb_ractor_shareable_p(val)) {
+                rb_raise(rb_eRactorIsolationError,
+                        "can not get unshareable values from instance variables of classes/modules from non-main Ractors");
+            }
+
+            return val;
+        }
+      default:
+        {
+            VALUE fields_obj = rb_obj_fields(obj, id);
+            return rb_imemo_fields_ptr(fields_obj)[index];
+        }
+    }
+}
+
+VALUE
 rb_attr_get(VALUE obj, ID id)
 {
     return rb_ivar_lookup(obj, id, Qnil);