From d1bd4e233cd4c06734173d532eb2215140b26357 Mon Sep 17 00:00:00 2001
From: Matt Valentine-House <matt@eightbitraptor.com>
Date: Tue, 30 Mar 2021 13:36:58 +0100
Subject: Store rb_classext_t next to RClass slots on the heap

---
 class.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

(limited to 'class.c')

diff --git a/class.c b/class.c
index e1e1ce0e7a..6784540a9e 100644
--- a/class.c
+++ b/class.c
@@ -173,8 +173,21 @@ rb_class_detach_module_subclasses(VALUE klass)
 static VALUE
 class_alloc(VALUE flags, VALUE klass)
 {
-    NEWOBJ_OF(obj, struct RClass, klass, (flags & T_MASK) | FL_PROMOTED1 /* start from age == 2 */ | (RGENGC_WB_PROTECTED_CLASS ? FL_WB_PROTECTED : 0));
+    size_t payload_size = 0;
+
+#if USE_RVARGC
+    payload_size = sizeof(rb_classext_t);
+#endif
+
+    RVARGC_NEWOBJ_OF(obj, struct RClass, klass, (flags & T_MASK) | FL_PROMOTED1 /* start from age == 2 */ | (RGENGC_WB_PROTECTED_CLASS ? FL_WB_PROTECTED : 0), payload_size);
+
+#if USE_RVARGC
+    obj->ptr = (rb_classext_t *)rb_rvargc_payload_data_ptr((VALUE)obj + rb_slot_size());
+    RB_OBJ_WRITTEN(obj, Qundef, (VALUE)obj + rb_slot_size());
+#else
     obj->ptr = ZALLOC(rb_classext_t);
+#endif
+
     /* ZALLOC
       RCLASS_IV_TBL(obj) = 0;
       RCLASS_CONST_TBL(obj) = 0;
-- 
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