From cae85c528c7c8ea1dd3ba634db5ccb9e465707f7 Mon Sep 17 00:00:00 2001
From: Alan Wu <XrXr@users.noreply.github.com>
Date: Thu, 5 May 2022 16:30:56 -0400
Subject: [PATCH] Mark RCLASS_INCLUDER

Since 4d8f76286beefbb8f7fba2479f6d0a0b4a47304c, we need to dereference
the includer field on iclasses, so we need to mark it to make sure
it's alive.

Sometimes during compaction we crash because the field is dangling,
though I have a hard time constructing such a situation. See
http://ci.rvm.jp/results/trunk@ruby-iga/3947725
---
 gc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/gc.c b/gc.c
index 22a1839fb3..3710bafce3 100644
--- a/gc.c
+++ b/gc.c
@@ -6994,6 +6994,10 @@ gc_mark_children(rb_objspace_t *objspace, VALUE obj)
             gc_mark(objspace, RCLASS_SUPER(obj));
         }
 	if (!RCLASS_EXT(obj)) break;
+
+        if (RCLASS_INCLUDER(obj)) {
+            gc_mark(objspace, RCLASS_INCLUDER(obj));
+        }
 	mark_m_tbl(objspace, RCLASS_CALLABLE_M_TBL(obj));
         cc_table_mark(objspace, obj);
 	break;