From f6dcab5f50bc3ab00b17d3ce84bd906b176baa7a Mon Sep 17 00:00:00 2001
From: Peter Zhu <peter@peterzhu.ca>
Date: Fri, 20 Sep 2024 10:52:43 -0400
Subject: [PATCH] Assert that objects in write barrier are not dead

---
 gc/default.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/gc/default.c b/gc/default.c
index addaf01fc2..65aacb70a3 100644
--- a/gc/default.c
+++ b/gc/default.c
@@ -6126,6 +6126,13 @@ rb_gc_impl_writebarrier(void *objspace_ptr, VALUE a, VALUE b)
         if (SPECIAL_CONST_P(b)) rb_bug("rb_gc_writebarrier: b is special const: %"PRIxVALUE, b);
     }
 
+    GC_ASSERT(RB_BUILTIN_TYPE(a) != T_NONE);
+    GC_ASSERT(RB_BUILTIN_TYPE(a) != T_MOVED);
+    GC_ASSERT(RB_BUILTIN_TYPE(a) != T_ZOMBIE);
+    GC_ASSERT(RB_BUILTIN_TYPE(b) != T_NONE);
+    GC_ASSERT(RB_BUILTIN_TYPE(b) != T_MOVED);
+    GC_ASSERT(RB_BUILTIN_TYPE(b) != T_ZOMBIE);
+
   retry:
     if (!is_incremental_marking(objspace)) {
         if (!RVALUE_OLD_P(objspace, a) || RVALUE_OLD_P(objspace, b)) {