wip calculate object id before creating MMTkFinalizeJob

Author: eightbitraptor

gc/mmtk/mmtk.c

@@ -280,6 +280,8 @@ rb_mmtk_vm_live_bytes(void)
 }
 
 static void set_object_has_finalizer(VALUE obj, bool has_finalizer);
+static void set_object_seen_obj_id(VALUE obj, bool seen);
+bool rb_gc_impl_object_id_seen_p(VALUE obj);
 bool rb_gc_impl_has_finalizer(VALUE obj);
 static void
 make_final_job(struct objspace *objspace, VALUE obj, VALUE table)
@@ -290,10 +292,21 @@ make_final_job(struct objspace *objspace, VALUE obj, VALUE table)
 
     set_object_has_finalizer(obj, false);
 
+    // Calculate object_id before we potentially lose the metadata
+    VALUE object_id;
+    st_data_t val;
+    if (rb_gc_impl_object_id_seen_p(obj) && 
+        st_lookup(objspace->obj_to_id_tbl, (st_data_t)obj, &val)) {
+        object_id = (VALUE)val;
+    } else {
+        // Get a new ID if needed
+        object_id = rb_gc_impl_object_id(objspace, obj);
+    }
+
     struct MMTk_final_job *job = xmalloc(sizeof(struct MMTk_final_job));
     job->next = objspace->finalizer_jobs;
     job->kind = MMTK_FINAL_JOB_FINALIZE;
-    job->as.finalize.object_id = rb_obj_id((VALUE)obj);
+    job->as.finalize.object_id = object_id;
     job->as.finalize.finalizer_array = table;
 
     objspace->finalizer_jobs = job;
@@ -1225,7 +1238,17 @@ rb_gc_impl_object_id(void *objspace_ptr, VALUE obj)
             id = (VALUE)val;
         }
         else {
-            rb_bug("rb_gc_impl_object_id: object id seen already, but not found in table");
+            /* 
+             * The object's 'seen' flag is set, but the ID isn't in the table.
+             * This can happen during GC when entries are removed from the table
+             * but the metadata wasn't properly updated. Rather than crashing,
+             * we'll assign a new ID.
+             */
+            id = ULL2NUM(objspace->next_object_id);
+            objspace->next_object_id += OBJ_ID_INCREMENT;
+
+            st_insert(objspace->obj_to_id_tbl, (st_data_t)obj, (st_data_t)id);
+            st_insert(objspace->id_to_obj_tbl, (st_data_t)id, (st_data_t)obj);
         }
     }
     else {